Messages in this thread Patch in this message | | | From | Edward Adam Davis <> | Subject | [PATCH] hfs: fix deadlock in hfs_extend_file | Date | Tue, 2 Jan 2024 20:36:51 +0800 |
| |
[syz report] syz-executor279/5059 is trying to acquire lock: ffff888079c100f8 (&HFS_I(tree->inode)->extents_lock){+.+.}-{3:3}, at: hfs_extend_file+0xa2/0xb10 fs/hfs/extent.c:397
but task is already holding lock: ffff888079c10778 (&HFS_I(tree->inode)->extents_lock){+.+.}-{3:3}, at: hfs_extend_file+0xa2/0xb10 fs/hfs/extent.c:397
other info that might help us debug this: Possible unsafe locking scenario:
CPU0 ---- lock(&HFS_I(tree->inode)->extents_lock); lock(&HFS_I(tree->inode)->extents_lock);
*** DEADLOCK *** [Analysis] hfs_extend_file()-> hfs_ext_read_extent()-> __hfs_ext_cache_extent()-> __hfs_ext_write_extent()-> hfs_bmap_reserve()-> hfs_extend_file()->
When an inode has both the HFS_FLG_EXT_DIRTY and HFS_FLG_EXT_NEW flags, it will enter the above loop and trigger a deadlock.
[Fix] In hfs_ext_read_extent(), check if the above two flags exist simultaneously, and exit the subsequent process when the conditions are met.
Reported-and-tested-by: syzbot+41a88b825a315aac2254@syzkaller.appspotmail.com Signed-off-by: Edward Adam Davis <eadavis@qq.com> --- fs/hfs/extent.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/fs/hfs/extent.c b/fs/hfs/extent.c index 6d1878b99b30..1b02c7b6a10c 100644 --- a/fs/hfs/extent.c +++ b/fs/hfs/extent.c @@ -197,6 +197,10 @@ static int hfs_ext_read_extent(struct inode *inode, u16 block) block < HFS_I(inode)->cached_start + HFS_I(inode)->cached_blocks) return 0; + if (HFS_I(inode)->flags & HFS_FLG_EXT_DIRTY && + HFS_I(inode)->flags & HFS_FLG_EXT_NEW) + return -ENOENT; + res = hfs_find_init(HFS_SB(inode->i_sb)->ext_tree, &fd); if (!res) { res = __hfs_ext_cache_extent(&fd, inode, block); -- 2.43.0
| |