linux-kernel - [PATCH] seccomp: cap SECCOMP_RET_ERRNO data to MAX

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20150206210309.GA32377@www.outflux.net>
Date:	Fri, 6 Feb 2015 13:03:09 -0800
From:	Kees Cook <keescook@...omium.org>
To:	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org,
	Andy Lutomirski <luto@...capital.net>,
	Will Drewry <wad@...omium.org>,
	"Dmitry V. Levin" <ldv@...linux.org>
Subject: [PATCH] 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.

Reported-by: Dmitry V. Levin <ldv@...linux.org>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 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 majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/