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erofs: fix race in z_erofs_get_gbuf()

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commit 7dc5537c3f upstream.

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: f36f3010f6 ("erofs: rename per-CPU buffers to global buffer pool and make it configurable")
Cc: <stable@vger.kernel.org> # 6.10+
Reviewed-by: Chunhai Guo <guochunhai@vivo.com>
Reviewed-by: Sandeep Dhavale <dhavale@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240722035110.3456740-1-hsiangkao@linux.alibaba.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Gao Xiang 2024-07-22 11:51:10 +08:00 committed by Greg Kroah-Hartman
parent 242cda6c45
commit 49b22e06a9
1 changed files with 3 additions and 0 deletions
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3
fs/erofs/zutil.c
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@ -38,11 +38,13 @@ void *z_erofs_get_gbuf(unsigned int requiredpages)
{
struct z_erofs_gbuf *gbuf;
migrate_disable();
gbuf = &z_erofs_gbufpool[z_erofs_gbuf_id()];
spin_lock(&gbuf->lock);
/* check if the buffer is too small */
if (requiredpages > gbuf->nrpages) {
spin_unlock(&gbuf->lock);
migrate_enable();
/* (for sparse checker) pretend gbuf->lock is still taken */
__acquire(gbuf->lock);
return NULL;
@ -57,6 +59,7 @@ void z_erofs_put_gbuf(void *ptr) __releases(gbuf->lock)
gbuf = &z_erofs_gbufpool[z_erofs_gbuf_id()];
DBG_BUGON(gbuf->ptr != ptr);
spin_unlock(&gbuf->lock);
migrate_enable();
}
int z_erofs_gbuf_growsize(unsigned int nrpages)