From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Paris Subject: RHEL4 panic when renaming with a watched file as the target Date: Mon, 05 Feb 2007 14:45:20 -0500 Message-ID: <1170704720.6447.77.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-audit-bounces@redhat.com Errors-To: linux-audit-bounces@redhat.com To: linux-audit@redhat.com, tinytim@us.ibm.com, sgrubb@redhat.com List-Id: linux-audit@redhat.com Since the upstream filesystem auditing is different than RHEL4 this problem (I believe) is RHEL4 specific. Lets assume I add the rule auditctl -w /tmp/watched_file then I run touch /tmp/unwatched_file mv -f /tmp/watched_file For the purposes of this discussion lets call the inode for the original /tmp/watched_file i1 and the indoe for the original /tmp/unwatched_fiel i2. The RHEL4 kernel panics. The reason is because it wants to allocate a audit_inode_data to i2 but there is no audit_inode_data to allocate. Thus we get the panic as seen in RH BZ 223129. When the watch was originally inserted the kernel mallocs 2 audit_inode_data structs. One for the inode to be watched and one for the parent of the that inode. In our case the panic happens because those 2 structs are allocated for i1 and for the inode associated with /tmp. From looking at the code I saw that in d_move we were dropping the audit_inode_data associated with i2 (inside that function i2 is pointed at by "dentry") at the beginning. But we were not dropping the watch on i1. It appears that the watch was intended to have been dropped on i1 later in i_put. At the end of d_move we add the watch for i2. It was at this point that things blew up (as i_put had not yet released the data structure.) My first attempt at fixing this simply was to change d_move such that it would drop the audit_inode_data for both i1 and i2 and then add it back to i2 once i2 was the inode which needed the watch. This however simply moved the panic into i_put when it wanted to remove the audit_inode_data from the original i1. The reason it panics there is because when trying to fetch the audit_inode_data to free it, it was actually trying to allocate a new struct so it had something to free! My solution simply passes a new flag to audit_data_get which states if the intent of requesting the audit_inode_data is to use it or to remove it. If the intent of getting the audit_inode_data was to simply remove that struct from the inode there is no need to allocate a new one just to have it removed. This patch appears to fix the panic and to correctly watch the correct inodes at the correct times. I'd love comment as there may be other solutions to either of the problems. Maybe we like the removal of the watch on i1 in d_move but we don't like the new flags. In that case we could just 'mess' around with i1 at the end of d_move such that it wouldn't watch the watch in i_put and wouldn't ever get into audit_data_get to cause the secondary panic. Maybe there is something I'm missing altogether. Anyway comments please before I put this into a RHEL4 kernel would be appreciated. -Eric diff -Naupr linux-2.6.9/fs/dcache.c linux-2.6.9/fs/dcache.c --- linux-2.6.9/fs/dcache.c 2007-02-05 13:12:01.000000000 -0500 +++ linux-2.6.9/fs/dcache.c 2007-02-05 13:09:36.000000000 -0500 @@ -1292,6 +1292,7 @@ void d_move(struct dentry * dentry, stru } audit_update_watch(dentry, 1); + audit_update_watch(target, 1); /* Move the dentry to the target hash queue, if on different bucket */ if (dentry->d_flags & DCACHE_UNHASHED) diff -Naupr linux-2.6.9/kernel/auditfs.c linux-2.6.9/kernel/auditfs.c --- linux-2.6.9/kernel/auditfs.c 2007-02-05 13:11:49.000000000 -0500 +++ linux-2.6.9/kernel/auditfs.c 2007-02-05 13:09:09.000000000 -0500 @@ -110,7 +110,8 @@ static void audit_data_pool_shrink(void) spin_unlock(&auditfs_hash_lock); } -static struct audit_inode_data *audit_data_get(struct inode *inode, int allocate) +static struct audit_inode_data *audit_data_get(struct inode *inode, int allocate, + int remove) { struct audit_inode_data **list; struct audit_inode_data *ret = NULL; @@ -142,7 +143,7 @@ static struct audit_inode_data *audit_da if (ret) { ret->count++; - } else if (allocate) { + } else if (allocate && !remove) { ret = audit_data_pool; audit_data_pool = ret->next_hash; audit_pool_size--; @@ -410,7 +411,7 @@ static inline int audit_insert_watch(str if (nd.last_type != LAST_NORM || !nd.last.name) goto release; - pdata = audit_data_get(nd.dentry->d_inode, 1); + pdata = audit_data_get(nd.dentry->d_inode, 1, 0); if (!pdata) goto put_pdata; @@ -478,7 +479,7 @@ static inline int audit_remove_watch(str if (nd.last_type != LAST_NORM || !nd.last.name) goto audit_remove_watch_release; - data = audit_data_get(nd.dentry->d_inode, 0); + data = audit_data_get(nd.dentry->d_inode, 0, 1); if (!data) goto audit_remove_watch_release; @@ -562,7 +563,7 @@ void audit_update_watch(struct dentry *d /* If there's no audit data on the parent inode, then there can be no watches to add or remove */ - parent = audit_data_get(dentry->d_parent->d_inode, 0); + parent = audit_data_get(dentry->d_parent->d_inode, 0, 0); if (!parent) return; @@ -571,7 +572,7 @@ void audit_update_watch(struct dentry *d /* Fetch audit data, using the preallocated one from the watch if there is actually a relevant watch and the inode didn't already have any audit data */ - data = audit_data_get(dentry->d_inode, !!watch); + data = audit_data_get(dentry->d_inode, !!watch, remove); /* If there's no data, then there wasn't a watch either. Nothing to see here; move along */ @@ -786,7 +787,7 @@ void audit_inode_free(struct inode *inod { struct audit_watch *watch; struct hlist_node *pos, *tmp; - struct audit_inode_data *data = audit_data_get(inode, 0); + struct audit_inode_data *data = audit_data_get(inode, 0, 1); if (data) { spin_lock(&auditfs_hash_lock); @@ -851,7 +852,7 @@ void audit_notify_watch(struct inode *in if (!inode || !current->audit_context) return; - data = audit_data_get(inode, 0); + data = audit_data_get(inode, 0, 0); if (!data) return;