minix/servers/vfs/protect.c

301 lines
8.5 KiB
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/* This file deals with protection in the file system. It contains the code
* for four system calls that relate to protection.
*
* The entry points into this file are
* do_chmod: perform the CHMOD and FCHMOD system calls
* do_chown: perform the CHOWN and FCHOWN system calls
* do_umask: perform the UMASK system call
* do_access: perform the ACCESS system call
*/
#include "fs.h"
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#include <sys/stat.h>
#include <unistd.h>
#include <assert.h>
#include <minix/callnr.h>
#include "file.h"
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#include "path.h"
#include <minix/vfsif.h>
#include "vnode.h"
#include "vmnt.h"
/*===========================================================================*
* do_chmod *
*===========================================================================*/
int do_chmod(void)
{
/* Perform the chmod(name, mode) and fchmod(fd, mode) system calls.
* syscall might provide 'name' embedded in the message.
*/
struct filp *flp;
Mostly bugfixes of bugs triggered by the test set. bugfixes: SYSTEM: . removed rc->p_priv->s_flags = 0; for the priv struct shared by all user processes in get_priv(). this should only be done once. doing a SYS_PRIV_USER in sys_privctl() caused the flags of all user processes to be reset, so they were no longer PREEMPTIBLE. this happened when RS executed a policy script. (this broke test1 in the test set) VFS/MFS: . chown can change the mode of a file, and chmod arguments are only part of the full file mode so the full filemode is slightly magic. changed these calls so that the final modes are returned to VFS, so that the vnode can be kept up-to-date. (this broke test11 in the test set) MFS: . lookup() checked for sizeof(string) instead of sizeof(user_path), truncating long path names (caught by test 23) . truncate functions neglected to update ctime (this broke test16) VFS: . corner case of an empty filename lookup caused fields of a request not to be filled in in the lookup functions, not making it clear that the lookup had failed, causing messages to garbage processes, causing strange failures. (caught by test 30) . trust v_size in vnode when doing reads or writes on non-special files, truncating i/o where necessary; this is necessary for pipes, as MFS can't tell when a pipe has been truncated without it being told explicitly each time. when the last reader/writer on a pipe closes, tell FS about the new size using truncate_vn(). (this broke test 25, among others) . permission check for chdir() had disappeared; added a forbidden() call (caught by test 23) new code, shouldn't change anything: . introduced RTS_SET, RTS_UNSET, and RTS_ISSET macro's, and their LOCK variants. These macros set and clear the p_rts_flags field, causing a lot of duplicated logic like old_flags = rp->p_rts_flags; /* save value of the flags */ rp->p_rts_flags &= ~NO_PRIV; if (old_flags != 0 && rp->p_rts_flags == 0) lock_enqueue(rp); to change into the simpler RTS_LOCK_UNSET(rp, NO_PRIV); so the macros take care of calling dequeue() and enqueue() (or lock_*()), as the case may be). This makes the code a bit more readable and a bit less fragile. . removed return code from do_clocktick in CLOCK as it currently never replies . removed some debug code from VFS . fixed grant debug message in device.c preemptive checks, tests, changes: . added return code checks of receive() to SYSTEM and CLOCK . O_TRUNC should never arrive at MFS (added sanity check and removed O_TRUNC code) . user_path declared with PATH_MAX+1 to let it be null-terminated . checks in MFS to see if strings passed by VFS are null-terminated IS: . static irq name table thrown out
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struct vnode *vp;
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struct vmnt *vmp;
int r, rfd;
mode_t result_mode;
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char fullpath[PATH_MAX];
struct lookup resolve;
mode_t new_mode;
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flp = NULL;
lookup_init(&resolve, fullpath, PATH_NOFLAGS, &vmp, &vp);
resolve.l_vmnt_lock = VMNT_READ;
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resolve.l_vnode_lock = VNODE_WRITE;
if (job_call_nr == VFS_CHMOD) {
new_mode = job_m_in.m_lc_vfs_path.mode;
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/* Temporarily open the file */
if (copy_path(fullpath, sizeof(fullpath)) != OK)
return(err_code);
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if ((vp = eat_path(&resolve, fp)) == NULL) return(err_code);
} else { /* call_nr == VFS_FCHMOD */
rfd = job_m_in.VFS_FCHMOD_FD;
new_mode = (mode_t) job_m_in.VFS_FCHMOD_MODE;
/* File is already opened; get a pointer to vnode from filp. */
if ((flp = get_filp(rfd, VNODE_WRITE)) == NULL) return(err_code);
vp = flp->filp_vno;
assert(vp);
dup_vnode(vp);
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}
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assert(vp);
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/* Only the owner or the super_user may change the mode of a file.
* No one may change the mode of a file on a read-only file system.
*/
if (vp->v_uid != fp->fp_effuid && fp->fp_effuid != SU_UID)
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r = EPERM;
else
r = read_only(vp);
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if (r == OK) {
/* Now make the change. Clear setgid bit if file is not in caller's
* group */
if (fp->fp_effuid != SU_UID && vp->v_gid != fp->fp_effgid)
new_mode &= ~I_SET_GID_BIT;
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r = req_chmod(vp->v_fs_e, vp->v_inode_nr, new_mode, &result_mode);
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if (r == OK)
vp->v_mode = result_mode;
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}
Mostly bugfixes of bugs triggered by the test set. bugfixes: SYSTEM: . removed rc->p_priv->s_flags = 0; for the priv struct shared by all user processes in get_priv(). this should only be done once. doing a SYS_PRIV_USER in sys_privctl() caused the flags of all user processes to be reset, so they were no longer PREEMPTIBLE. this happened when RS executed a policy script. (this broke test1 in the test set) VFS/MFS: . chown can change the mode of a file, and chmod arguments are only part of the full file mode so the full filemode is slightly magic. changed these calls so that the final modes are returned to VFS, so that the vnode can be kept up-to-date. (this broke test11 in the test set) MFS: . lookup() checked for sizeof(string) instead of sizeof(user_path), truncating long path names (caught by test 23) . truncate functions neglected to update ctime (this broke test16) VFS: . corner case of an empty filename lookup caused fields of a request not to be filled in in the lookup functions, not making it clear that the lookup had failed, causing messages to garbage processes, causing strange failures. (caught by test 30) . trust v_size in vnode when doing reads or writes on non-special files, truncating i/o where necessary; this is necessary for pipes, as MFS can't tell when a pipe has been truncated without it being told explicitly each time. when the last reader/writer on a pipe closes, tell FS about the new size using truncate_vn(). (this broke test 25, among others) . permission check for chdir() had disappeared; added a forbidden() call (caught by test 23) new code, shouldn't change anything: . introduced RTS_SET, RTS_UNSET, and RTS_ISSET macro's, and their LOCK variants. These macros set and clear the p_rts_flags field, causing a lot of duplicated logic like old_flags = rp->p_rts_flags; /* save value of the flags */ rp->p_rts_flags &= ~NO_PRIV; if (old_flags != 0 && rp->p_rts_flags == 0) lock_enqueue(rp); to change into the simpler RTS_LOCK_UNSET(rp, NO_PRIV); so the macros take care of calling dequeue() and enqueue() (or lock_*()), as the case may be). This makes the code a bit more readable and a bit less fragile. . removed return code from do_clocktick in CLOCK as it currently never replies . removed some debug code from VFS . fixed grant debug message in device.c preemptive checks, tests, changes: . added return code checks of receive() to SYSTEM and CLOCK . O_TRUNC should never arrive at MFS (added sanity check and removed O_TRUNC code) . user_path declared with PATH_MAX+1 to let it be null-terminated . checks in MFS to see if strings passed by VFS are null-terminated IS: . static irq name table thrown out
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if (job_call_nr == VFS_CHMOD) {
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unlock_vnode(vp);
unlock_vmnt(vmp);
} else { /* VFS_FCHMOD */
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unlock_filp(flp);
}
Mostly bugfixes of bugs triggered by the test set. bugfixes: SYSTEM: . removed rc->p_priv->s_flags = 0; for the priv struct shared by all user processes in get_priv(). this should only be done once. doing a SYS_PRIV_USER in sys_privctl() caused the flags of all user processes to be reset, so they were no longer PREEMPTIBLE. this happened when RS executed a policy script. (this broke test1 in the test set) VFS/MFS: . chown can change the mode of a file, and chmod arguments are only part of the full file mode so the full filemode is slightly magic. changed these calls so that the final modes are returned to VFS, so that the vnode can be kept up-to-date. (this broke test11 in the test set) MFS: . lookup() checked for sizeof(string) instead of sizeof(user_path), truncating long path names (caught by test 23) . truncate functions neglected to update ctime (this broke test16) VFS: . corner case of an empty filename lookup caused fields of a request not to be filled in in the lookup functions, not making it clear that the lookup had failed, causing messages to garbage processes, causing strange failures. (caught by test 30) . trust v_size in vnode when doing reads or writes on non-special files, truncating i/o where necessary; this is necessary for pipes, as MFS can't tell when a pipe has been truncated without it being told explicitly each time. when the last reader/writer on a pipe closes, tell FS about the new size using truncate_vn(). (this broke test 25, among others) . permission check for chdir() had disappeared; added a forbidden() call (caught by test 23) new code, shouldn't change anything: . introduced RTS_SET, RTS_UNSET, and RTS_ISSET macro's, and their LOCK variants. These macros set and clear the p_rts_flags field, causing a lot of duplicated logic like old_flags = rp->p_rts_flags; /* save value of the flags */ rp->p_rts_flags &= ~NO_PRIV; if (old_flags != 0 && rp->p_rts_flags == 0) lock_enqueue(rp); to change into the simpler RTS_LOCK_UNSET(rp, NO_PRIV); so the macros take care of calling dequeue() and enqueue() (or lock_*()), as the case may be). This makes the code a bit more readable and a bit less fragile. . removed return code from do_clocktick in CLOCK as it currently never replies . removed some debug code from VFS . fixed grant debug message in device.c preemptive checks, tests, changes: . added return code checks of receive() to SYSTEM and CLOCK . O_TRUNC should never arrive at MFS (added sanity check and removed O_TRUNC code) . user_path declared with PATH_MAX+1 to let it be null-terminated . checks in MFS to see if strings passed by VFS are null-terminated IS: . static irq name table thrown out
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put_vnode(vp);
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return(r);
}
/*===========================================================================*
* do_chown *
*===========================================================================*/
int do_chown(void)
{
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/* Perform the chown(path, owner, group) and fchmod(fd, owner, group) system
* calls. */
struct filp *flp;
Mostly bugfixes of bugs triggered by the test set. bugfixes: SYSTEM: . removed rc->p_priv->s_flags = 0; for the priv struct shared by all user processes in get_priv(). this should only be done once. doing a SYS_PRIV_USER in sys_privctl() caused the flags of all user processes to be reset, so they were no longer PREEMPTIBLE. this happened when RS executed a policy script. (this broke test1 in the test set) VFS/MFS: . chown can change the mode of a file, and chmod arguments are only part of the full file mode so the full filemode is slightly magic. changed these calls so that the final modes are returned to VFS, so that the vnode can be kept up-to-date. (this broke test11 in the test set) MFS: . lookup() checked for sizeof(string) instead of sizeof(user_path), truncating long path names (caught by test 23) . truncate functions neglected to update ctime (this broke test16) VFS: . corner case of an empty filename lookup caused fields of a request not to be filled in in the lookup functions, not making it clear that the lookup had failed, causing messages to garbage processes, causing strange failures. (caught by test 30) . trust v_size in vnode when doing reads or writes on non-special files, truncating i/o where necessary; this is necessary for pipes, as MFS can't tell when a pipe has been truncated without it being told explicitly each time. when the last reader/writer on a pipe closes, tell FS about the new size using truncate_vn(). (this broke test 25, among others) . permission check for chdir() had disappeared; added a forbidden() call (caught by test 23) new code, shouldn't change anything: . introduced RTS_SET, RTS_UNSET, and RTS_ISSET macro's, and their LOCK variants. These macros set and clear the p_rts_flags field, causing a lot of duplicated logic like old_flags = rp->p_rts_flags; /* save value of the flags */ rp->p_rts_flags &= ~NO_PRIV; if (old_flags != 0 && rp->p_rts_flags == 0) lock_enqueue(rp); to change into the simpler RTS_LOCK_UNSET(rp, NO_PRIV); so the macros take care of calling dequeue() and enqueue() (or lock_*()), as the case may be). This makes the code a bit more readable and a bit less fragile. . removed return code from do_clocktick in CLOCK as it currently never replies . removed some debug code from VFS . fixed grant debug message in device.c preemptive checks, tests, changes: . added return code checks of receive() to SYSTEM and CLOCK . O_TRUNC should never arrive at MFS (added sanity check and removed O_TRUNC code) . user_path declared with PATH_MAX+1 to let it be null-terminated . checks in MFS to see if strings passed by VFS are null-terminated IS: . static irq name table thrown out
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struct vnode *vp;
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struct vmnt *vmp;
int r, rfd;
uid_t uid, new_uid;
gid_t gid, new_gid;
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mode_t new_mode;
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char fullpath[PATH_MAX];
struct lookup resolve;
vir_bytes vname1;
size_t vname1_length;
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flp = NULL;
uid = job_m_in.m_lc_vfs_chown.owner;
gid = job_m_in.m_lc_vfs_chown.group;
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if (job_call_nr == VFS_CHOWN) {
vname1 = job_m_in.m_lc_vfs_chown.name;
vname1_length = job_m_in.m_lc_vfs_chown.len;
lookup_init(&resolve, fullpath, PATH_NOFLAGS, &vmp, &vp);
resolve.l_vmnt_lock = VMNT_READ;
resolve.l_vnode_lock = VNODE_WRITE;
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/* Temporarily open the file. */
if (fetch_name(vname1, vname1_length, fullpath) != OK)
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return(err_code);
if ((vp = eat_path(&resolve, fp)) == NULL) return(err_code);
} else { /* call_nr == VFS_FCHOWN */
rfd = job_m_in.m_lc_vfs_chown.fd;
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/* File is already opened; get a pointer to the vnode from filp. */
if ((flp = get_filp(rfd, VNODE_WRITE)) == NULL)
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return(err_code);
vp = flp->filp_vno;
dup_vnode(vp);
}
Various VFS and MFS fixes to improve correctness, consistency and POSIX compliance. VFS changes: * truncate() on a file system mounted read-only no longer panics MFS. * ftruncate() and fcntl(F_FREESP) now check for write permission on the file descriptor instead of the file, write(). * utime(), chown() and fchown() now check for file system read-only status. MFS changes: * link() and rename() no longer return the internal EENTERMOUNT and ELEAVEMOUNT errors to the application as part of a check on the source path. * rename() now treats EENTERMOUNT from the destination path check as an error, preventing file system corruption from renaming a normal directory to an existing mountpoint directory. * mountpoints (mounted-on dirs) are hidden better during lookups: - if a lookup starts from a mountpoint, the first component has to be ".." (anything else being a VFS-FS protocol violation). - in that case, the permissions of the mountpoint are not checked. - in all other cases, visiting a mountpoint always results in EENTERMOUNT. * a lookup on ".." from a mount root or chroot(2) root no longer succeeds if the caller does not have search permission on that directory. * POSIX: getdents() now updates directory access times. * POSIX: readlink() now returns partial results instead of ERANGE. Miscellaneous changes: * semaphore file handling bug (leading to hangs) fixed in test 32. The VFS changes should now put the burden of checking for read-only status of file systems entirely on VFS, and limit the access permission checks that file systems have to perform, to checking search permission on directories during lookups. From this point on, any deviation from that spceification should be considered a bug. Note that for legacy reasons, the root partition is assumed to be mounted read-write.
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r = read_only(vp);
if (r == OK) {
/* FS is R/W. Whether call is allowed depends on ownership, etc. */
/* The super user can do anything, so check permissions only if we're
a regular user. */
if (fp->fp_effuid != SU_UID) {
/* Regular users can only change groups of their own files. */
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if (vp->v_uid != fp->fp_effuid) r = EPERM;
if (vp->v_uid != uid) r = EPERM; /* no giving away */
if (fp->fp_effgid != gid) r = EPERM;
}
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}
Mostly bugfixes of bugs triggered by the test set. bugfixes: SYSTEM: . removed rc->p_priv->s_flags = 0; for the priv struct shared by all user processes in get_priv(). this should only be done once. doing a SYS_PRIV_USER in sys_privctl() caused the flags of all user processes to be reset, so they were no longer PREEMPTIBLE. this happened when RS executed a policy script. (this broke test1 in the test set) VFS/MFS: . chown can change the mode of a file, and chmod arguments are only part of the full file mode so the full filemode is slightly magic. changed these calls so that the final modes are returned to VFS, so that the vnode can be kept up-to-date. (this broke test11 in the test set) MFS: . lookup() checked for sizeof(string) instead of sizeof(user_path), truncating long path names (caught by test 23) . truncate functions neglected to update ctime (this broke test16) VFS: . corner case of an empty filename lookup caused fields of a request not to be filled in in the lookup functions, not making it clear that the lookup had failed, causing messages to garbage processes, causing strange failures. (caught by test 30) . trust v_size in vnode when doing reads or writes on non-special files, truncating i/o where necessary; this is necessary for pipes, as MFS can't tell when a pipe has been truncated without it being told explicitly each time. when the last reader/writer on a pipe closes, tell FS about the new size using truncate_vn(). (this broke test 25, among others) . permission check for chdir() had disappeared; added a forbidden() call (caught by test 23) new code, shouldn't change anything: . introduced RTS_SET, RTS_UNSET, and RTS_ISSET macro's, and their LOCK variants. These macros set and clear the p_rts_flags field, causing a lot of duplicated logic like old_flags = rp->p_rts_flags; /* save value of the flags */ rp->p_rts_flags &= ~NO_PRIV; if (old_flags != 0 && rp->p_rts_flags == 0) lock_enqueue(rp); to change into the simpler RTS_LOCK_UNSET(rp, NO_PRIV); so the macros take care of calling dequeue() and enqueue() (or lock_*()), as the case may be). This makes the code a bit more readable and a bit less fragile. . removed return code from do_clocktick in CLOCK as it currently never replies . removed some debug code from VFS . fixed grant debug message in device.c preemptive checks, tests, changes: . added return code checks of receive() to SYSTEM and CLOCK . O_TRUNC should never arrive at MFS (added sanity check and removed O_TRUNC code) . user_path declared with PATH_MAX+1 to let it be null-terminated . checks in MFS to see if strings passed by VFS are null-terminated IS: . static irq name table thrown out
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if (r == OK) {
/* Do not change uid/gid if new uid/gid is -1. */
new_uid = (uid == (uid_t)-1 ? vp->v_uid : uid);
new_gid = (gid == (gid_t)-1 ? vp->v_gid : gid);
if (new_uid > UID_MAX || new_gid > GID_MAX)
r = EINVAL;
else if ((r = req_chown(vp->v_fs_e, vp->v_inode_nr, new_uid, new_gid,
&new_mode)) == OK) {
vp->v_uid = new_uid;
vp->v_gid = new_gid;
vp->v_mode = new_mode;
}
Mostly bugfixes of bugs triggered by the test set. bugfixes: SYSTEM: . removed rc->p_priv->s_flags = 0; for the priv struct shared by all user processes in get_priv(). this should only be done once. doing a SYS_PRIV_USER in sys_privctl() caused the flags of all user processes to be reset, so they were no longer PREEMPTIBLE. this happened when RS executed a policy script. (this broke test1 in the test set) VFS/MFS: . chown can change the mode of a file, and chmod arguments are only part of the full file mode so the full filemode is slightly magic. changed these calls so that the final modes are returned to VFS, so that the vnode can be kept up-to-date. (this broke test11 in the test set) MFS: . lookup() checked for sizeof(string) instead of sizeof(user_path), truncating long path names (caught by test 23) . truncate functions neglected to update ctime (this broke test16) VFS: . corner case of an empty filename lookup caused fields of a request not to be filled in in the lookup functions, not making it clear that the lookup had failed, causing messages to garbage processes, causing strange failures. (caught by test 30) . trust v_size in vnode when doing reads or writes on non-special files, truncating i/o where necessary; this is necessary for pipes, as MFS can't tell when a pipe has been truncated without it being told explicitly each time. when the last reader/writer on a pipe closes, tell FS about the new size using truncate_vn(). (this broke test 25, among others) . permission check for chdir() had disappeared; added a forbidden() call (caught by test 23) new code, shouldn't change anything: . introduced RTS_SET, RTS_UNSET, and RTS_ISSET macro's, and their LOCK variants. These macros set and clear the p_rts_flags field, causing a lot of duplicated logic like old_flags = rp->p_rts_flags; /* save value of the flags */ rp->p_rts_flags &= ~NO_PRIV; if (old_flags != 0 && rp->p_rts_flags == 0) lock_enqueue(rp); to change into the simpler RTS_LOCK_UNSET(rp, NO_PRIV); so the macros take care of calling dequeue() and enqueue() (or lock_*()), as the case may be). This makes the code a bit more readable and a bit less fragile. . removed return code from do_clocktick in CLOCK as it currently never replies . removed some debug code from VFS . fixed grant debug message in device.c preemptive checks, tests, changes: . added return code checks of receive() to SYSTEM and CLOCK . O_TRUNC should never arrive at MFS (added sanity check and removed O_TRUNC code) . user_path declared with PATH_MAX+1 to let it be null-terminated . checks in MFS to see if strings passed by VFS are null-terminated IS: . static irq name table thrown out
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}
if (job_call_nr == VFS_CHOWN) {
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unlock_vnode(vp);
unlock_vmnt(vmp);
} else { /* VFS_FCHOWN */
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unlock_filp(flp);
}
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put_vnode(vp);
return(r);
}
/*===========================================================================*
* do_umask *
*===========================================================================*/
int do_umask(void)
{
/* Perform the umask(2) system call. */
mode_t complement, new_umask;
new_umask = job_m_in.m_lc_vfs_umask.mask;
complement = ~fp->fp_umask; /* set 'r' to complement of old mask */
fp->fp_umask = ~(new_umask & RWX_MODES);
return(complement); /* return complement of old mask */
}
/*===========================================================================*
* do_access *
*===========================================================================*/
int do_access(void)
{
/* Perform the access(name, mode) system call.
* syscall might provide 'name' embedded in the message.
*/
int r;
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struct vnode *vp;
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struct vmnt *vmp;
char fullpath[PATH_MAX];
struct lookup resolve;
mode_t access;
access = job_m_in.m_lc_vfs_path.mode;
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lookup_init(&resolve, fullpath, PATH_NOFLAGS, &vmp, &vp);
resolve.l_vmnt_lock = VMNT_READ;
resolve.l_vnode_lock = VNODE_READ;
/* First check to see if the mode is correct. */
if ( (access & ~(R_OK | W_OK | X_OK)) != 0 && access != F_OK)
return(EINVAL);
/* Temporarily open the file. */
if (copy_path(fullpath, sizeof(fullpath)) != OK)
return(err_code);
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if ((vp = eat_path(&resolve, fp)) == NULL) return(err_code);
r = forbidden(fp, vp, access);
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unlock_vnode(vp);
unlock_vmnt(vmp);
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put_vnode(vp);
return(r);
}
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/*===========================================================================*
* forbidden *
*===========================================================================*/
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int forbidden(struct fproc *rfp, struct vnode *vp, mode_t access_desired)
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{
/* Given a pointer to an vnode, 'vp', and the access desired, determine
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* if the access is allowed, and if not why not. The routine looks up the
* caller's uid in the 'fproc' table. If access is allowed, OK is returned
* if it is forbidden, EACCES is returned.
*/
register mode_t bits, perm_bits;
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uid_t uid;
gid_t gid;
int r, shift;
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if (vp->v_uid == (uid_t) -1 || vp->v_gid == (gid_t) -1) return(EACCES);
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/* Isolate the relevant rwx bits from the mode. */
bits = vp->v_mode;
uid = (job_call_nr == VFS_ACCESS ? rfp->fp_realuid : rfp->fp_effuid);
gid = (job_call_nr == VFS_ACCESS ? rfp->fp_realgid : rfp->fp_effgid);
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if (uid == SU_UID) {
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/* Grant read and write permission. Grant search permission for
* directories. Grant execute permission (for non-directories) if
* and only if one of the 'X' bits is set.
*/
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if ( S_ISDIR(bits) || bits & ((X_BIT << 6) | (X_BIT << 3) | X_BIT))
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perm_bits = R_BIT | W_BIT | X_BIT;
else
perm_bits = R_BIT | W_BIT;
} else {
if (uid == vp->v_uid) shift = 6; /* owner */
else if (gid == vp->v_gid) shift = 3; /* group */
else if (in_group(fp, vp->v_gid) == OK) shift = 3; /* suppl. groups */
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else shift = 0; /* other */
perm_bits = (bits >> shift) & (R_BIT | W_BIT | X_BIT);
}
/* If access desired is not a subset of what is allowed, it is refused. */
r = OK;
if ((perm_bits | access_desired) != perm_bits) r = EACCES;
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/* Check to see if someone is trying to write on a file system that is
* mounted read-only.
*/
if (r == OK)
if (access_desired & W_BIT)
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r = read_only(vp);
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return(r);
}
/*===========================================================================*
* read_only *
*===========================================================================*/
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int read_only(vp)
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struct vnode *vp; /* ptr to inode whose file sys is to be cked */
{
/* Check to see if the file system on which the inode 'ip' resides is mounted
* read only. If so, return EROFS, else return OK.
*/
assert(vp);
return(vp->v_vmnt && (vp->v_vmnt->m_flags & VMNT_READONLY) ? EROFS : OK);
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}