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exportfs: do not read dentry after free 

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>
This commit is contained in:
Pan Bian 2018-11-23 15:56:33 +08:00 committed by Al Viro
parent 909e22e053
commit 2084ac6c50
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);
dput(dentry);
if (IS_ROOT(dentry)) {
if (dentry == parent) {
dput(parent);
return false;
}