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authorDavidlohr Bueso <dave@stgolabs.net>2018-04-10 16:35:26 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-04-11 10:28:37 -0700
commita280d6dc77eb6002f269d58cd47c7c7e69b617b6 (patch)
tree312545b1f84f43d8cb8aba2168a8ad32eac09cb8 /include
parentc21a6970ae727839a2f300cd8dd957de0d0238c3 (diff)
ipc/sem: introduce semctl(SEM_STAT_ANY)
There is a permission discrepancy when consulting shm ipc object metadata between /proc/sysvipc/sem (0444) and the SEM_STAT semctl command. The later does permission checks for the object vs S_IRUGO. As such there can be cases where EACCESS is returned via syscall but the info is displayed anyways in the procfs files. While this might have security implications via info leaking (albeit no writing to the sma metadata), this behavior goes way back and showing all the objects regardless of the permissions was most likely an overlook - so we are stuck with it. Furthermore, modifying either the syscall or the procfs file can cause userspace programs to break (ie ipcs). Some applications require getting the procfs info (without root privileges) and can be rather slow in comparison with a syscall -- up to 500x in some reported cases for shm. This patch introduces a new SEM_STAT_ANY command such that the sem ipc object permissions are ignored, and only audited instead. In addition, I've left the lsm security hook checks in place, as if some policy can block the call, then the user has no other choice than just parsing the procfs file. Link: http://lkml.kernel.org/r/20180215162458.10059-3-dave@stgolabs.net Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Reported-by: Robert Kettler <robert.kettler@outlook.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Kees Cook <keescook@chromium.org> Cc: Manfred Spraul <manfred@colorfullife.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/uapi/linux/sem.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/uapi/linux/sem.h b/include/uapi/linux/sem.h
index 9c3e745b0656..39a1876f039e 100644
--- a/include/uapi/linux/sem.h
+++ b/include/uapi/linux/sem.h
@@ -19,6 +19,7 @@
/* ipcs ctl cmds */
#define SEM_STAT 18
#define SEM_INFO 19
+#define SEM_STAT_ANY 20
/* Obsolete, used only for backwards compatibility and libc5 compiles */
struct semid_ds {