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From: Alexey Dobriyan <adobriyan@gmail.com>
To: akpm@linux-foundation.org
Cc: linux-kernel@vger.kernel.org, gorcunov@openvz.org, security@kernel.org
Subject: [PATCH] prctl: fix PR_SET_MM_AUXV kernel stack leak
Date: Sun, 14 Mar 2021 23:51:14 +0300	[thread overview]
Message-ID: <YE53QiJuxsCUeoiu@localhost.localdomain> (raw)

	prctl(PR_SET_MM, PR_SET_MM_AUXV, addr, 1);

will copy 1 byte from userspace to (quite big) on-stack array
and then stash everything to mm->saved_auxv.
AT_NULL terminator will be inserted at the very end.

/proc/*/auxv handler will find that AT_NULL terminator
and copy original stack contents to userspace.

This devious scheme requires CAP_SYS_RESOURCE.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

	apply to >=3.5

 kernel/sys.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2079,7 +2079,7 @@ static int prctl_set_auxv(struct mm_struct *mm, unsigned long addr,
 	 * up to the caller to provide sane values here, otherwise userspace
 	 * tools which use this vector might be unhappy.
 	 */
-	unsigned long user_auxv[AT_VECTOR_SIZE];
+	unsigned long user_auxv[AT_VECTOR_SIZE] = {};
 
 	if (len > sizeof(user_auxv))
 		return -EINVAL;

             reply	other threads:[~2021-03-14 20:52 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-14 20:51 Alexey Dobriyan [this message]
2021-03-14 21:40 ` Linus Torvalds
2021-03-14 22:24   ` Cyrill Gorcunov
2021-03-15  6:00   ` auxv stuff (Re: [PATCH] prctl: fix PR_SET_MM_AUXV kernel stack leak) Alexey Dobriyan
2021-03-15  6:42     ` Cyrill Gorcunov
2021-03-16 18:50       ` Alexey Dobriyan
2021-03-16 18:51         ` Cyrill Gorcunov
2021-03-14 22:18 ` [PATCH] prctl: fix PR_SET_MM_AUXV kernel stack leak Cyrill Gorcunov
2021-03-15 10:29 ` Dan Carpenter
2021-03-15 13:30   ` Alexey Dobriyan
2021-03-15 12:08 ` Oleg Nesterov
2021-03-15 12:54   ` Cyrill Gorcunov
2021-03-15 13:19     ` Oleg Nesterov
2021-03-15 13:52       ` Cyrill Gorcunov

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