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Message-Id: <20210315135214.162644461@linuxfoundation.org>
Date: Mon, 15 Mar 2021 14:52:27 +0100
From: gregkh@...uxfoundation.org
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Alexey Dobriyan <adobriyan@...il.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 64/78] prctl: fix PR_SET_MM_AUXV kernel stack leak
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
From: Alexey Dobriyan <adobriyan@...il.com>
[ Upstream commit c995f12ad8842dbf5cfed113fb52cdd083f5afd1 ]
Doing a
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@...il.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
kernel/sys.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sys.c b/kernel/sys.c
index 546cdc911dad..76b3d9262644 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1910,7 +1910,7 @@ 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;
--
2.30.1
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