[PATCH] Yama: verify inode is symlink to avoid bind mounts
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From: Kees Cook on 13 Jul 2010 18:40 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(a)canonical.com> --- security/yama/yama_lsm.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c index 3b76386..c70eb10 100644 --- a/security/yama/yama_lsm.c +++ b/security/yama/yama_lsm.c @@ -116,6 +116,10 @@ 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 */ + if (!S_ISLNK(inode->i_mode)) + return 0; + /* owner and follower match? */ cred = current_cred(); inode = dentry->d_inode; -- 1.7.1 -- Kees Cook Ubuntu Security Team -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |