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exportfs: do not read dentry after free

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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>
This commit is contained in:
Pan Bian
2018-11-23 15:56:33 +08:00
committed by Greg Kroah-Hartman
parent 0aeda30045
commit ad374d10b7
1 changed files with 1 additions and 1 deletions
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2
fs/exportfs/expfs.c
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@@ -77,7 +77,7 @@ static bool dentry_connected(struct dentry *dentry)
struct dentry *parent = dget_parent(dentry); struct dentry *parent = dget_parent(dentry);
dput(dentry); dput(dentry);
if (IS_ROOT(dentry)) { if (dentry == parent) {
dput(parent); dput(parent);
return false; return false;
} }