From 982f7c2b2e6a28f8f266e075d92e19c0dd4c6e56 Mon Sep 17 00:00:00 2001 From: Dan Rosenberg Date: Thu, 30 Sep 2010 15:15:31 -0700 Subject: [PATCH] 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 Cc: Manfred Spraul Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- ipc/sem.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/ipc/sem.c b/ipc/sem.c index 40a8f462a822..0e0d49bbb867 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -743,6 +743,8 @@ static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, { struct semid_ds out; + memset(&out, 0, sizeof(out)); + ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm); out.sem_otime = in->sem_otime; -- 2.20.1