seccomp: cap SECCOMP_RET_ERRNO data to MAX_ERRNO

The value resulting from the SECCOMP_RET_DATA mask could exceed MAX_ERRNO when setting errno during a SECCOMP_RET_ERRNO filter action. This makes sure we have a reliable value being set, so that an invalid errno will not be ignored by userspace. Signed-off-by: Kees Cook <[email protected]> Reported-by: Dmitry V. Levin <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Will Drewry <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
vieko · Feb 17, 2015 · 580c57f · 580c57f
1 parent 3a9af0b
commit 580c57f
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
@@ -629,7 +629,9 @@ static u32 __seccomp_phase1_filter(int this_syscall, struct seccomp_data *sd)
 
 	switch (action) {
 	case SECCOMP_RET_ERRNO:
-		/* Set the low-order 16-bits as a errno. */
+		/* Set low-order bits as an errno, capped at MAX_ERRNO. */
+		if (data > MAX_ERRNO)
+			data = MAX_ERRNO;
 		syscall_set_return_value(current, task_pt_regs(current),
 					 -data, 0);
 		goto skip;