]> pilppa.com Git - linux-2.6-omap-h63xx.git/commit
fix setuid sometimes doesn't
authorHugh Dickins <hugh@veritas.com>
Sat, 28 Mar 2009 23:20:19 +0000 (23:20 +0000)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sun, 29 Mar 2009 00:30:00 +0000 (17:30 -0700)
commite426b64c412aaa3e9eb3e4b261dc5be0d5a83e78
treec1528139b34fef3e4595576266c64068098fe211
parent53e9309e01277ec99c38e84e0ca16921287cf470
fix setuid sometimes doesn't

Joe Malicki reports that setuid sometimes doesn't: very rarely,
a setuid root program does not get root euid; and, by the way,
they have a health check running lsof every few minutes.

Right, check_unsafe_exec() notes whether the files_struct is being
shared by more threads than will get killed by the exec, and if so
sets LSM_UNSAFE_SHARE to make bprm_set_creds() careful about euid.
But /proc/<pid>/fd and /proc/<pid>/fdinfo lookups make transient
use of get_files_struct(), which also raises that sharing count.

There's a rather simple fix for this: exec's check on files->count
has been redundant ever since 2.6.1 made it unshare_files() (except
while compat_do_execve() omitted to do so) - just remove that check.

[Note to -stable: this patch will not apply before 2.6.29: earlier
releases should just remove the files->count line from unsafe_exec().]

Reported-by: Joe Malicki <jmalicki@metacarta.com>
Narrowed-down-by: Michael Itz <mitz@metacarta.com>
Tested-by: Joe Malicki <jmalicki@metacarta.com>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/compat.c
fs/exec.c
fs/internal.h