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.
Reported-by: Dmitry V. Levin <[email protected]> Signed-off-by: Kees Cook <[email protected]> --- kernel/seccomp.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 4ef9687ac115..4f44028943e6 100644 --- 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; -- 1.9.1 -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
