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From: Michal Hocko <mhocko@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
	Michal Hocko <mhocko@suse.com>, Kees Cook <keescook@chromium.org>,
	Vlastimil Babka <vbabka@suse.cz>
Subject: [PATCH 5/9] xattr: zero out memory copied to userspace in getxattr
Date: Mon,  6 Mar 2017 11:33:23 +0100
Message-ID: <20170306103327.2766-1-mhocko@kernel.org> (raw)
In-Reply-To: <20170306103032.2540-1-mhocko@kernel.org>

From: Michal Hocko <mhocko@suse.com>

getxattr uses vmalloc to allocate memory if kzalloc fails. This is
filled by vfs_getxattr and then copied to the userspace. vmalloc,
however, doesn't zero out the memory so if the specific implementation
of the xattr handler is sloppy we can theoretically expose a kernel
memory. There is no real sign this is really the case but let's make
sure this will not happen and use vzalloc instead.

Fixes: 779302e67835 ("fs/xattr.c:getxattr(): improve handling of allocation failures")
Cc: stable # 3.6+
Acked-by: Kees Cook <keescook@chromium.org>
Spotted-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 fs/xattr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/xattr.c b/fs/xattr.c
index 7e3317cf4045..94f49a082dd2 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -530,7 +530,7 @@ getxattr(struct dentry *d, const char __user *name, void __user *value,
 			size = XATTR_SIZE_MAX;
 		kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
 		if (!kvalue) {
-			kvalue = vmalloc(size);
+			kvalue = vzalloc(size);
 			if (!kvalue)
 				return -ENOMEM;
 		}
-- 
2.11.0

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  parent reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-06 10:30 [PATCH 0/6 v5] kvmalloc Michal Hocko
2017-03-06 10:30 ` [PATCH 1/9] mm: introduce kv[mz]alloc helpers Michal Hocko
2017-06-02  7:17   ` Levin, Alexander (Sasha Levin)
2017-06-02  7:28     ` Michal Hocko
2017-06-02  7:40       ` Levin, Alexander (Sasha Levin)
2017-06-02  7:50         ` Michal Hocko
2017-03-06 10:30 ` [PATCH 2/9] mm: support __GFP_REPEAT in kvmalloc_node for >32kB Michal Hocko
2017-04-07  0:45   ` Shakeel Butt
2017-04-07  7:40     ` Michal Hocko
2017-03-06 10:30 ` [PATCH 3/9] rhashtable: simplify a strange allocation pattern Michal Hocko
2017-03-06 10:30 ` [PATCH 4/9] ila: " Michal Hocko
2017-03-06 10:33 ` Michal Hocko [this message]
2017-03-06 10:33   ` [PATCH 6/9] treewide: use kv[mz]alloc* rather than opencoded variants Michal Hocko
2017-03-06 10:33   ` [PATCH 7/9] net: use kvmalloc with __GFP_REPEAT rather than open coded variant Michal Hocko
2017-03-30 23:21     ` Shakeel Butt
2017-03-31  8:46       ` Michal Hocko
2017-03-06 10:33   ` [PATCH 8/9] md: use kvmalloc rather than opencoded variant Michal Hocko
2017-03-06 10:33   ` [PATCH 9/9] bcache: use kvmalloc Michal Hocko

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