linux-kernel - [tip:sched/urgent] sched: Fix information leak in sys_sched

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Date:	Fri, 21 Feb 2014 12:32:26 -0800
From:	tip-bot for Vegard Nossum <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	peterz@...radead.org, raistlin@...ux.it, vegard.nossum@...cle.com,
	tglx@...utronix.de, juri.lelli@...il.com
Subject: [tip:sched/urgent] sched:
  Fix information leak in sys_sched_getattr()

Commit-ID:  4efbc454ba68def5ef285b26ebfcfdb605b52755
Gitweb:     http://git.kernel.org/tip/4efbc454ba68def5ef285b26ebfcfdb605b52755
Author:     Vegard Nossum <vegard.nossum@...cle.com>
AuthorDate: Sun, 16 Feb 2014 22:24:17 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 21 Feb 2014 21:27:10 +0100

sched: Fix information leak in sys_sched_getattr()

We're copying the on-stack structure to userspace, but forgot to give
the right number of bytes to copy. This allows the calling process to
obtain up to PAGE_SIZE bytes from the stack (and possibly adjacent
kernel memory).

This fix copies only as much as we actually have on the stack
(attr->size defaults to the size of the struct) and leaves the rest of
the userspace-provided buffer untouched.

Found using kmemcheck + trinity.

Fixes: d50dde5a10f30 ("sched: Add new scheduler syscalls to support an extended scheduling parameters ABI")
Cc: Dario Faggioli <raistlin@...ux.it>
Cc: Juri Lelli <juri.lelli@...il.com>
Cc: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Vegard Nossum <vegard.nossum@...cle.com>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/1392585857-10725-1-git-send-email-vegard.nossum@oracle.com
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/sched/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 33d030a..a6e7470 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3786,7 +3786,7 @@ static int sched_read_attr(struct sched_attr __user *uattr,
 		attr->size = usize;
 	}
 
-	ret = copy_to_user(uattr, attr, usize);
+	ret = copy_to_user(uattr, attr, attr->size);
 	if (ret)
 		return -EFAULT;
 
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