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ovl: Add comment on upperredirect reassignment

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If memory for uperredirect was allocated with kstrdup() in upperdir != NULL
and d.redirect != NULL path, it may seem that it can be lost when
upperredirect is reassigned later, but it's not possible.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 0a2d0d3f2f ("ovl: Check redirect on index as well")
Signed-off-by: Stanislav Goriainov <goriainov@ispras.ru>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Stanislav Goriainov 2022-08-31 11:06:58 +03:00 • committed by Miklos Szeredi
parent af4dcb6d78
commit cf4ef7801a
1 changed files with 5 additions and 0 deletions
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5
fs/overlayfs/namei.c
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@ -1086,6 +1086,11 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
.mnt = ovl_upper_mnt(ofs),
};
/*
* It's safe to assign upperredirect here: the previous
* assignment of happens only if upperdentry is non-NULL, and
* this one only if upperdentry is NULL.
*/
upperredirect = ovl_get_redirect_xattr(ofs, &upperpath, 0);
if (IS_ERR(upperredirect)) {
err = PTR_ERR(upperredirect);