4.9-stable review patch. If anyone has any objections, please let me know.
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[ 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 a4b531be9168..7a7bba7c2328 100644 --- a/fs/exportfs/expfs.c +++ b/fs/exportfs/expfs.c @@ -76,7 +76,7 @@ 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; }