[PATCH] hfsplus: fix to avoid false alarm of circular locking

From: Chao Yu
Date: Fri Jun 07 2024 - 10:23:35 EST

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Syzbot report potential ABBA deadlock as below:

loop0: detected capacity change from 0 to 1024
======================================================
WARNING: possible circular locking dependency detected
6.9.0-syzkaller-10323-g8f6a15f095a6 #0 Not tainted
------------------------------------------------------
syz-executor171/5344 is trying to acquire lock:
ffff88807cb980b0 (&tree->tree_lock){+.+.}-{3:3}, at: hfsplus_file_truncate+0x811/0xb50 fs/hfsplus/extents.c:595

but task is already holding lock:
ffff88807a930108 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{3:3}, at: hfsplus_file_truncate+0x2da/0xb50 fs/hfsplus/extents.c:576

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{3:3}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
hfsplus_file_extend+0x21b/0x1b70 fs/hfsplus/extents.c:457
hfsplus_bmap_reserve+0x105/0x4e0 fs/hfsplus/btree.c:358
hfsplus_rename_cat+0x1d0/0x1050 fs/hfsplus/catalog.c:456
hfsplus_rename+0x12e/0x1c0 fs/hfsplus/dir.c:552
vfs_rename+0xbdb/0xf00 fs/namei.c:4887
do_renameat2+0xd94/0x13f0 fs/namei.c:5044
__do_sys_rename fs/namei.c:5091 [inline]
__se_sys_rename fs/namei.c:5089 [inline]
__x64_sys_rename+0x86/0xa0 fs/namei.c:5089
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tree->tree_lock){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
hfsplus_file_truncate+0x811/0xb50 fs/hfsplus/extents.c:595
hfsplus_setattr+0x1ce/0x280 fs/hfsplus/inode.c:265
notify_change+0xb9d/0xe70 fs/attr.c:497
do_truncate+0x220/0x310 fs/open.c:65
handle_truncate fs/namei.c:3308 [inline]
do_open fs/namei.c:3654 [inline]
path_openat+0x2a3d/0x3280 fs/namei.c:3807
do_filp_open+0x235/0x490 fs/namei.c:3834
do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
do_sys_open fs/open.c:1421 [inline]
__do_sys_creat fs/open.c:1497 [inline]
__se_sys_creat fs/open.c:1491 [inline]
__x64_sys_creat+0x123/0x170 fs/open.c:1491
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&HFSPLUS_I(inode)->extents_lock);
lock(&tree->tree_lock);
lock(&HFSPLUS_I(inode)->extents_lock);
lock(&tree->tree_lock);

This is a false alarm as tree_lock mutex are different, one is
from sbi->cat_tree, and another is from sbi->ext_tree:

Thread A Thread B
- hfsplus_rename
- hfsplus_rename_cat
- hfs_find_init
- mutext_lock(cat_tree->tree_lock)
- hfsplus_setattr
- hfsplus_file_truncate
- mutex_lock(hip->extents_lock)
- hfs_find_init
- mutext_lock(ext_tree->tree_lock)
- hfs_bmap_reserve
- hfsplus_file_extend
- mutex_lock(hip->extents_lock)

So, let's call mutex_lock_nested for tree_lock mutex lock, and pass
correct lock class for it.

Fixes: 31651c607151 ("hfsplus: avoid deadlock on file truncation")
Reported-by: syzbot+6030b3b1b9bf70e538c4@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://lore.kernel.org/linux-fsdevel/000000000000e37a4005ef129563@xxxxxxxxxx
Cc: Ernesto A. Fernández <ernesto.mnd.fernandez@xxxxxxxxx>
Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
---
fs/hfsplus/bfind.c | 15 ++-------------
fs/hfsplus/extents.c | 9 ++++++---
fs/hfsplus/hfsplus_fs.h | 21 +++++++++++++++++++++
3 files changed, 29 insertions(+), 16 deletions(-)

diff --git a/fs/hfsplus/bfind.c b/fs/hfsplus/bfind.c
index ca2ba8c9f82e..901e83d65d20 100644
--- a/fs/hfsplus/bfind.c
+++ b/fs/hfsplus/bfind.c
@@ -25,19 +25,8 @@ int hfs_find_init(struct hfs_btree *tree, struct hfs_find_data *fd)
fd->key = ptr + tree->max_key_len + 2;
hfs_dbg(BNODE_REFS, "find_init: %d (%p)\n",
tree->cnid, __builtin_return_address(0));
- switch (tree->cnid) {
- case HFSPLUS_CAT_CNID:
- mutex_lock_nested(&tree->tree_lock, CATALOG_BTREE_MUTEX);
- break;
- case HFSPLUS_EXT_CNID:
- mutex_lock_nested(&tree->tree_lock, EXTENTS_BTREE_MUTEX);
- break;
- case HFSPLUS_ATTR_CNID:
- mutex_lock_nested(&tree->tree_lock, ATTR_BTREE_MUTEX);
- break;
- default:
- BUG();
- }
+ mutex_lock_nested(&tree->tree_lock,
+ hfsplus_btree_lock_class(tree));
return 0;
}

diff --git a/fs/hfsplus/extents.c b/fs/hfsplus/extents.c
index 3c572e44f2ad..9c51867dddc5 100644
--- a/fs/hfsplus/extents.c
+++ b/fs/hfsplus/extents.c
@@ -430,7 +430,8 @@ int hfsplus_free_fork(struct super_block *sb, u32 cnid,
hfsplus_free_extents(sb, ext_entry, total_blocks - start,
total_blocks);
total_blocks = start;
- mutex_lock(&fd.tree->tree_lock);
+ mutex_lock_nested(&fd.tree->tree_lock,
+ hfsplus_btree_lock_class(fd.tree));
} while (total_blocks > blocks);
hfs_find_exit(&fd);

@@ -592,7 +593,8 @@ void hfsplus_file_truncate(struct inode *inode)
alloc_cnt, alloc_cnt - blk_cnt);
hfsplus_dump_extent(hip->first_extents);
hip->first_blocks = blk_cnt;
- mutex_lock(&fd.tree->tree_lock);
+ mutex_lock_nested(&fd.tree->tree_lock,
+ hfsplus_btree_lock_class(fd.tree));
break;
}
res = __hfsplus_ext_cache_extent(&fd, inode, alloc_cnt);
@@ -606,7 +608,8 @@ void hfsplus_file_truncate(struct inode *inode)
hfsplus_free_extents(sb, hip->cached_extents,
alloc_cnt - start, alloc_cnt - blk_cnt);
hfsplus_dump_extent(hip->cached_extents);
- mutex_lock(&fd.tree->tree_lock);
+ mutex_lock_nested(&fd.tree->tree_lock,
+ hfsplus_btree_lock_class(fd.tree));
if (blk_cnt > start) {
hip->extent_state |= HFSPLUS_EXT_DIRTY;
break;
diff --git a/fs/hfsplus/hfsplus_fs.h b/fs/hfsplus/hfsplus_fs.h
index 012a3d003fbe..9e78f181c24f 100644
--- a/fs/hfsplus/hfsplus_fs.h
+++ b/fs/hfsplus/hfsplus_fs.h
@@ -553,6 +553,27 @@ static inline __be32 __hfsp_ut2mt(time64_t ut)
return cpu_to_be32(lower_32_bits(ut) + HFSPLUS_UTC_OFFSET);
}

+static inline enum hfsplus_btree_mutex_classes
+hfsplus_btree_lock_class(struct hfs_btree *tree)
+{
+ enum hfsplus_btree_mutex_classes class;
+
+ switch (tree->cnid) {
+ case HFSPLUS_CAT_CNID:
+ class = CATALOG_BTREE_MUTEX;
+ break;
+ case HFSPLUS_EXT_CNID:
+ class = EXTENTS_BTREE_MUTEX;
+ break;
+ case HFSPLUS_ATTR_CNID:
+ class = ATTR_BTREE_MUTEX;
+ break;
+ default:
+ BUG();
+ }
+ return class;
+}
+
/* compatibility */
#define hfsp_mt2ut(t) (struct timespec64){ .tv_sec = __hfsp_mt2ut(t) }
#define hfsp_ut2mt(t) __hfsp_ut2mt((t).tv_sec)
--
2.40.1

Next message: Haitao Huang: "Re: [PATCH v14 02/14] cgroup/misc: Add per resource callbacks for CSS events"
Previous message: Rafael J. Wysocki: "Re: [PATCH 1/1] cpufreq: Rewire arch specific feedback for cpuinfo/scaling_cur_freq"
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