6.12-stable review patch. If anyone has any objections, please let me know.
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From: Gao Xiang hsiangkao@linux.alibaba.com
commit b10a1e5643e505c367c7e16aa6d8a9a0dc07354b upstream.
There may still exist some pcluster with valid reference counts during unmounting. Instead of introducing another synchronization primitive, just try again as unmounting is relatively rare. This approach is similar to z_erofs_cache_invalidate_folio().
It was also reported by syzbot as a UAF due to commit f5ad9f9a603f ("erofs: free pclusters if no cached folio is attached"):
BUG: KASAN: slab-use-after-free in do_raw_spin_trylock+0x72/0x1f0 kernel/locking/spinlock_debug.c:123 .. queued_spin_trylock include/asm-generic/qspinlock.h:92 [inline] do_raw_spin_trylock+0x72/0x1f0 kernel/locking/spinlock_debug.c:123 __raw_spin_trylock include/linux/spinlock_api_smp.h:89 [inline] _raw_spin_trylock+0x20/0x80 kernel/locking/spinlock.c:138 spin_trylock include/linux/spinlock.h:361 [inline] z_erofs_put_pcluster fs/erofs/zdata.c:959 [inline] z_erofs_decompress_pcluster fs/erofs/zdata.c:1403 [inline] z_erofs_decompress_queue+0x3798/0x3ef0 fs/erofs/zdata.c:1425 z_erofs_decompressqueue_work+0x99/0xe0 fs/erofs/zdata.c:1437 process_one_work kernel/workqueue.c:3229 [inline] process_scheduled_works+0xa68/0x1840 kernel/workqueue.c:3310 worker_thread+0x870/0xd30 kernel/workqueue.c:3391 kthread+0x2f2/0x390 kernel/kthread.c:389 ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 </TASK>
However, it seems a long outstanding memory leak. Fix it now.
Fixes: f5ad9f9a603f ("erofs: free pclusters if no cached folio is attached") Reported-by: syzbot+7ff87b095e7ca0c5ac39@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/674c1235.050a0220.ad585.0032.GAE@google.com Reviewed-by: Chao Yu chao@kernel.org Signed-off-by: Gao Xiang hsiangkao@linux.alibaba.com Link: https://lore.kernel.org/r/20241203072821.1885740-1-hsiangkao@linux.alibaba.c... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/erofs/zutil.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
--- a/fs/erofs/zutil.c +++ b/fs/erofs/zutil.c @@ -230,9 +230,10 @@ void erofs_shrinker_unregister(struct su struct erofs_sb_info *const sbi = EROFS_SB(sb);
mutex_lock(&sbi->umount_mutex); - /* clean up all remaining pclusters in memory */ - z_erofs_shrink_scan(sbi, ~0UL); - + while (!xa_empty(&sbi->managed_pslots)) { + z_erofs_shrink_scan(sbi, ~0UL); + cond_resched(); + } spin_lock(&erofs_sb_list_lock); list_del(&sbi->list); spin_unlock(&erofs_sb_list_lock);