| From a818101d7b92e76db2f9a597e4830734767473b9 Mon Sep 17 00:00:00 2001 |
| From: David Howells <dhowells@redhat.com> |
| Date: Tue, 9 Aug 2016 17:41:16 +0100 |
| Subject: cachefiles: Fix attempt to read i_blocks after deleting file [ver #2] |
| |
| From: David Howells <dhowells@redhat.com> |
| |
| commit a818101d7b92e76db2f9a597e4830734767473b9 upstream. |
| |
| An NULL-pointer dereference happens in cachefiles_mark_object_inactive() |
| when it tries to read i_blocks so that it can tell the cachefilesd daemon |
| how much space it's making available. |
| |
| The problem is that cachefiles_drop_object() calls |
| cachefiles_mark_object_inactive() after calling cachefiles_delete_object() |
| because the object being marked active staves off attempts to (re-)use the |
| file at that filename until after it has been deleted. This means that |
| d_inode is NULL by the time we come to try to access it. |
| |
| To fix the problem, have the caller of cachefiles_mark_object_inactive() |
| supply the number of blocks freed up. |
| |
| Without this, the following oops may occur: |
| |
| BUG: unable to handle kernel NULL pointer dereference at 0000000000000098 |
| IP: [<ffffffffa06c5cc1>] cachefiles_mark_object_inactive+0x61/0xb0 [cachefiles] |
| ... |
| CPU: 11 PID: 527 Comm: kworker/u64:4 Tainted: G I ------------ 3.10.0-470.el7.x86_64 #1 |
| Hardware name: Hewlett-Packard HP Z600 Workstation/0B54h, BIOS 786G4 v03.19 03/11/2011 |
| Workqueue: fscache_object fscache_object_work_func [fscache] |
| task: ffff880035edaf10 ti: ffff8800b77c0000 task.ti: ffff8800b77c0000 |
| RIP: 0010:[<ffffffffa06c5cc1>] cachefiles_mark_object_inactive+0x61/0xb0 [cachefiles] |
| RSP: 0018:ffff8800b77c3d70 EFLAGS: 00010246 |
| RAX: 0000000000000000 RBX: ffff8800bf6cc400 RCX: 0000000000000034 |
| RDX: 0000000000000000 RSI: ffff880090ffc710 RDI: ffff8800bf761ef8 |
| RBP: ffff8800b77c3d88 R08: 2000000000000000 R09: 0090ffc710000000 |
| R10: ff51005d2ff1c400 R11: 0000000000000000 R12: ffff880090ffc600 |
| R13: ffff8800bf6cc520 R14: ffff8800bf6cc400 R15: ffff8800bf6cc498 |
| FS: 0000000000000000(0000) GS:ffff8800bb8c0000(0000) knlGS:0000000000000000 |
| CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b |
| CR2: 0000000000000098 CR3: 00000000019ba000 CR4: 00000000000007e0 |
| DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 |
| DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 |
| Stack: |
| ffff880090ffc600 ffff8800bf6cc400 ffff8800867df140 ffff8800b77c3db0 |
| ffffffffa06c48cb ffff880090ffc600 ffff880090ffc180 ffff880090ffc658 |
| ffff8800b77c3df0 ffffffffa085d846 ffff8800a96b8150 ffff880090ffc600 |
| Call Trace: |
| [<ffffffffa06c48cb>] cachefiles_drop_object+0x6b/0xf0 [cachefiles] |
| [<ffffffffa085d846>] fscache_drop_object+0xd6/0x1e0 [fscache] |
| [<ffffffffa085d615>] fscache_object_work_func+0xa5/0x200 [fscache] |
| [<ffffffff810a605b>] process_one_work+0x17b/0x470 |
| [<ffffffff810a6e96>] worker_thread+0x126/0x410 |
| [<ffffffff810a6d70>] ? rescuer_thread+0x460/0x460 |
| [<ffffffff810ae64f>] kthread+0xcf/0xe0 |
| [<ffffffff810ae580>] ? kthread_create_on_node+0x140/0x140 |
| [<ffffffff81695418>] ret_from_fork+0x58/0x90 |
| [<ffffffff810ae580>] ? kthread_create_on_node+0x140/0x140 |
| |
| The oopsing code shows: |
| |
| callq 0xffffffff810af6a0 <wake_up_bit> |
| mov 0xf8(%r12),%rax |
| mov 0x30(%rax),%rax |
| mov 0x98(%rax),%rax <---- oops here |
| lock add %rax,0x130(%rbx) |
| |
| where this is: |
| |
| d_backing_inode(object->dentry)->i_blocks |
| |
| Fixes: a5b3a80b899bda0f456f1246c4c5a1191ea01519 (CacheFiles: Provide read-and-reset release counters for cachefilesd) |
| Reported-by: Jianhong Yin <jiyin@redhat.com> |
| Signed-off-by: David Howells <dhowells@redhat.com> |
| Reviewed-by: Jeff Layton <jlayton@redhat.com> |
| Reviewed-by: Steve Dickson <steved@redhat.com> |
| Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| fs/cachefiles/interface.c | 8 +++++++- |
| fs/cachefiles/internal.h | 3 ++- |
| fs/cachefiles/namei.c | 8 ++++---- |
| 3 files changed, 13 insertions(+), 6 deletions(-) |
| |
| --- a/fs/cachefiles/interface.c |
| +++ b/fs/cachefiles/interface.c |
| @@ -253,6 +253,8 @@ static void cachefiles_drop_object(struc |
| struct cachefiles_object *object; |
| struct cachefiles_cache *cache; |
| const struct cred *saved_cred; |
| + struct inode *inode; |
| + blkcnt_t i_blocks = 0; |
| |
| ASSERT(_object); |
| |
| @@ -279,6 +281,10 @@ static void cachefiles_drop_object(struc |
| _object != cache->cache.fsdef |
| ) { |
| _debug("- retire object OBJ%x", object->fscache.debug_id); |
| + inode = d_backing_inode(object->dentry); |
| + if (inode) |
| + i_blocks = inode->i_blocks; |
| + |
| cachefiles_begin_secure(cache, &saved_cred); |
| cachefiles_delete_object(cache, object); |
| cachefiles_end_secure(cache, saved_cred); |
| @@ -292,7 +298,7 @@ static void cachefiles_drop_object(struc |
| |
| /* note that the object is now inactive */ |
| if (test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags)) |
| - cachefiles_mark_object_inactive(cache, object); |
| + cachefiles_mark_object_inactive(cache, object, i_blocks); |
| |
| dput(object->dentry); |
| object->dentry = NULL; |
| --- a/fs/cachefiles/internal.h |
| +++ b/fs/cachefiles/internal.h |
| @@ -160,7 +160,8 @@ extern char *cachefiles_cook_key(const u |
| * namei.c |
| */ |
| extern void cachefiles_mark_object_inactive(struct cachefiles_cache *cache, |
| - struct cachefiles_object *object); |
| + struct cachefiles_object *object, |
| + blkcnt_t i_blocks); |
| extern int cachefiles_delete_object(struct cachefiles_cache *cache, |
| struct cachefiles_object *object); |
| extern int cachefiles_walk_to_object(struct cachefiles_object *parent, |
| --- a/fs/cachefiles/namei.c |
| +++ b/fs/cachefiles/namei.c |
| @@ -261,10 +261,9 @@ requeue: |
| * Mark an object as being inactive. |
| */ |
| void cachefiles_mark_object_inactive(struct cachefiles_cache *cache, |
| - struct cachefiles_object *object) |
| + struct cachefiles_object *object, |
| + blkcnt_t i_blocks) |
| { |
| - blkcnt_t i_blocks = d_backing_inode(object->dentry)->i_blocks; |
| - |
| write_lock(&cache->active_lock); |
| rb_erase(&object->active_node, &cache->active_nodes); |
| clear_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags); |
| @@ -707,7 +706,8 @@ mark_active_timed_out: |
| |
| check_error: |
| _debug("check error %d", ret); |
| - cachefiles_mark_object_inactive(cache, object); |
| + cachefiles_mark_object_inactive( |
| + cache, object, d_backing_inode(object->dentry)->i_blocks); |
| release_dentry: |
| dput(object->dentry); |
| object->dentry = NULL; |