fs: Check for invalid i_uid in may_follow_link()
Filesystem uids which don't map into a user namespace may result in inode->i_uid being INVALID_UID. A symlink and its parent could have different owners in the filesystem can both get mapped to INVALID_UID, which may result in following a symlink when this would not have otherwise been permitted when protected symlinks are enabled. Signed-off-by: Seth Forshee <seth.forshee@canonical.com> Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
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@ -901,6 +901,7 @@ static inline int may_follow_link(struct nameidata *nd)
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{
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const struct inode *inode;
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const struct inode *parent;
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kuid_t puid;
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if (!sysctl_protected_symlinks)
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return 0;
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@ -916,7 +917,8 @@ static inline int may_follow_link(struct nameidata *nd)
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return 0;
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/* Allowed if parent directory and link owner match. */
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if (uid_eq(parent->i_uid, inode->i_uid))
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puid = parent->i_uid;
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if (uid_valid(puid) && uid_eq(puid, inode->i_uid))
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return 0;
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if (nd->flags & LOOKUP_RCU)
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