| From | Sasha Levin <> | Subject | [PATCH AUTOSEL 4.14 31/69] exportfs: do not read dentry after free | Date | Wed, 5 Dec 2018 04:42:09 -0500 |
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From: Pan Bian <bianpan2016@163.com>
[ Upstream commit 2084ac6c505a58f7efdec13eba633c6aaa085ca5 ]
The function dentry_connected calls dput(dentry) to drop the previously acquired reference to dentry. In this case, dentry can be released. After that, IS_ROOT(dentry) checks the condition (dentry == dentry->d_parent), which may result in a use-after-free bug. This patch directly compares dentry with its parent obtained before dropping the reference.
Fixes: a056cc8934c("exportfs: stop retrying once we race with rename/remove")
Signed-off-by: Pan Bian <bianpan2016@163.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Sasha Levin <sashal@kernel.org> --- fs/exportfs/expfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c index 329a5d103846..c22cc9d2a5c9 100644 --- a/fs/exportfs/expfs.c +++ b/fs/exportfs/expfs.c @@ -77,7 +77,7 @@ static bool dentry_connected(struct dentry *dentry) struct dentry *parent = dget_parent(dentry); dput(dentry); - if (IS_ROOT(dentry)) { + if (dentry == parent) { dput(parent); return false; } -- 2.17.1
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