Messages in this thread Patch in this message | | | Date | Tue, 13 Jul 2010 23:18:45 -0700 | From | Kees Cook <> | Subject | [PATCH v2] Yama: verify inode is symlink to avoid bind mounts |
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The inode_follow_link LSM hook is called in bind mount situations as well as for symlink situations, so we must explicitly check for the inode being a symlink to not reject bind mounts in 1777 directories, which seems to be a common NFSv4 configuration.
Signed-off-by: Kees Cook <kees.cook@canonical.com> --- v2: - actually set inode in time to use it. *face palm* --- security/yama/yama_lsm.c | 6 +++++- 1 files changed, 5 insertions(+), 1 deletions(-)
diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c index 3b76386..51c6a3a 100644 --- a/security/yama/yama_lsm.c +++ b/security/yama/yama_lsm.c @@ -116,9 +116,13 @@ static int yama_inode_follow_link(struct dentry *dentry, if (!protected_sticky_symlinks) return 0; + /* if inode isn't a symlink, don't try to evaluate blocking it */ + inode = dentry->d_inode; + if (!S_ISLNK(inode->i_mode)) + return 0; + /* owner and follower match? */ cred = current_cred(); - inode = dentry->d_inode; if (cred->fsuid == inode->i_uid) return 0; -- 1.7.1
-- Kees Cook Ubuntu Security Team
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