sys_semctl: fix kernel stack leakage
authorDan Rosenberg <drosenberg@vsecurity.com>
Thu, 30 Sep 2010 22:15:31 +0000 (15:15 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 1 Oct 2010 17:50:58 +0000 (10:50 -0700)
commit982f7c2b2e6a28f8f266e075d92e19c0dd4c6e56
treea25ab8534b9f43cb90292ed125dfb9d72fee9858
parent64aab720bdf8771214a7c88872bd8e3194c2d279
sys_semctl: fix kernel stack leakage

The semctl syscall has several code paths that lead to the leakage of
uninitialized kernel stack memory (namely the IPC_INFO, SEM_INFO,
IPC_STAT, and SEM_STAT commands) during the use of the older, obsolete
version of the semid_ds struct.

The copy_semid_to_user() function declares a semid_ds struct on the stack
and copies it back to the user without initializing or zeroing the
"sem_base", "sem_pending", "sem_pending_last", and "undo" pointers,
allowing the leakage of 16 bytes of kernel stack memory.

The code is still reachable on 32-bit systems - when calling semctl()
newer glibc's automatically OR the IPC command with the IPC_64 flag, but
invoking the syscall directly allows users to use the older versions of
the struct.

Signed-off-by: Dan Rosenberg <dan.j.rosenberg@gmail.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
ipc/sem.c