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sys_semctl: fix kernel stack leakage

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commit 982f7c2b2e upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Dan Rosenberg 2010-09-30 15:15:31 -07:00 committed by Greg Kroah-Hartman
parent cebb2f20e0
commit 5572adc7b7
1 changed files with 2 additions and 0 deletions
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2
ipc/sem.c
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@ -608,6 +608,8 @@ static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in,
{ {
struct semid_ds out; struct semid_ds out;
memset(&out, 0, sizeof(out));
ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm); ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
out.sem_otime = in->sem_otime; out.sem_otime = in->sem_otime;