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Subjectsetfs[ug]id syscall return value and include/linux/security.h question
Hi!

Before include/linux/security.h was added, setfsuid/setfsgid always returned
old_fsuid, no matter if the fsuid was actually changed or not.
With the default security ops it seems to do the same, because both
security_task_setuid and security_task_post_setuid return 0, but these are
hooks which seem to return 0 on success, -errno on failure, so if some
non-default security hook is installed and ever returns -errno
in setfsuid/setfsgid, -errno will be returned from the syscall instead
of the expected old_fsuid. This makes it hard to distinguish uids
0xfffff001 .. 0xffffffff from errors of security hooks.
Shouldn't sys_setfsuid/sys_setfsgid be changed:
--- linux-2.5.66/kernel/sys.c.jj Mon Mar 24 23:00:00 2003
+++ linux-2.5.66/kernel/sys.c Thu Mar 27 00:11:20 2003
@@ -824,13 +824,11 @@ asmlinkage long sys_getresgid(gid_t *rgi
asmlinkage long sys_setfsuid(uid_t uid)
{
int old_fsuid;
- int retval;
-
- retval = security_task_setuid(uid, (uid_t)-1, (uid_t)-1, LSM_SETID_FS);
- if (retval)
- return retval;

old_fsuid = current->fsuid;
+ if (security_task_setuid(uid, (uid_t)-1, (uid_t)-1, LSM_SETID_FS))
+ return old_fsuid;
+
if (uid == current->uid || uid == current->euid ||
uid == current->suid || uid == current->fsuid ||
capable(CAP_SETUID))
@@ -843,9 +841,7 @@ asmlinkage long sys_setfsuid(uid_t uid)
current->fsuid = uid;
}

- retval = security_task_post_setuid(old_fsuid, (uid_t)-1, (uid_t)-1, LSM_SETID_FS);
- if (retval)
- return retval;
+ security_task_post_setuid(old_fsuid, (uid_t)-1, (uid_t)-1, LSM_SETID_FS);

return old_fsuid;
}
@@ -856,13 +852,11 @@ asmlinkage long sys_setfsuid(uid_t uid)
asmlinkage long sys_setfsgid(gid_t gid)
{
int old_fsgid;
- int retval;
-
- retval = security_task_setgid(gid, (gid_t)-1, (gid_t)-1, LSM_SETID_FS);
- if (retval)
- return retval;

old_fsgid = current->fsgid;
+ if (security_task_setgid(gid, (gid_t)-1, (gid_t)-1, LSM_SETID_FS))
+ return old_fsgid;
+
if (gid == current->gid || gid == current->egid ||
gid == current->sgid || gid == current->fsgid ||
capable(CAP_SETGID))
Jakub
-
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