Re: [PATCH] erofs: fix race in z_erofs_get_gbuf()

[Chao Yu]

On 2024/7/22 11:51, Gao Xiang wrote:
> In z_erofs_get_gbuf(), the current task may be migrated to another
> CPU between `z_erofs_gbuf_id()` and `spin_lock(&gbuf->lock)`.
>
> Therefore, z_erofs_put_gbuf() will trigger the following issue
> which was found by stress test:
>
> <2>[772156.434168] kernel BUG at fs/erofs/zutil.c:58!
> ..
> <4>[772156.435007]
> <4>[772156.439237] CPU: 0 PID: 3078 Comm: stress Kdump: loaded Tainted: G            E      6.10.0-rc7+ #2
> <4>[772156.439239] Hardware name: Alibaba Cloud Alibaba Cloud ECS, BIOS 1.0.0 01/01/2017
> <4>[772156.439241] pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
> <4>[772156.439243] pc : z_erofs_put_gbuf+0x64/0x70 [erofs]
> <4>[772156.439252] lr : z_erofs_lz4_decompress+0x600/0x6a0 [erofs]
> ..
> <6>[772156.445958] stress (3127): drop_caches: 1
> <4>[772156.446120] Call trace:
> <4>[772156.446121]  z_erofs_put_gbuf+0x64/0x70 [erofs]
> <4>[772156.446761]  z_erofs_lz4_decompress+0x600/0x6a0 [erofs]
> <4>[772156.446897]  z_erofs_decompress_queue+0x740/0xa10 [erofs]
> <4>[772156.447036]  z_erofs_runqueue+0x428/0x8c0 [erofs]
> <4>[772156.447160]  z_erofs_readahead+0x224/0x390 [erofs]
> ..
>
> Fixes: f36f3010f676 ("erofs: rename per-CPU buffers to global buffer pool and make it configurable")
> Cc: <stable@xxxxxxxxxxxxxxx> # 6.10+
> Cc: Chunhai Guo <guochunhai@xxxxxxxx>
> Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>

Reviewed-by: Chao Yu <chao@xxxxxxxxxx>

Thanks,