[ 40/52] Yama: handle 32-bit userspace prctl

[Greg Kroah-Hartman]

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kees Cook <keescook@xxxxxxxxxxxx>

commit 2e4930eb7c8fb20a39dfb5f8a8f80402710dcea8 upstream.

When running a 64-bit kernel and receiving prctls from a 32-bit
userspace, the "-1" used as an unsigned long will end up being
misdetected. The kernel is looking for 0xffffffffffffffff instead of
0xffffffff. Since prctl lacks a distinct compat interface, Yama needs
to handle this translation itself. As such, support either value as
meaning PR_SET_PTRACER_ANY, to avoid breaking the ABI for 64-bit.

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: John Johansen <john.johansen@xxxxxxxxxxxxx>
Signed-off-by: James Morris <james.l.morris@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 security/yama/yama_lsm.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -138,7 +138,7 @@ static int yama_task_prctl(int option, u
 		if (arg2 == 0) {
 			yama_ptracer_del(NULL, myself);
 			rc = 0;
-		} else if (arg2 == PR_SET_PTRACER_ANY) {
+		} else if (arg2 == PR_SET_PTRACER_ANY || (int)arg2 == -1) {
 			rc = yama_ptracer_add(NULL, myself);
 		} else {
 			struct task_struct *tracer;


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