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author | Gao Xiang <hsiangkao@linux.alibaba.com> | 2021-11-04 02:20:06 +0800 |
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committer | Gao Xiang <hsiangkao@linux.alibaba.com> | 2021-11-08 10:02:10 +0800 |
commit | 86432a6dca9bed79111990851df5756d3eb5f57c (patch) | |
tree | b7b99ac4e2ecf2ceff6b3d4a7fe0c8a66aba35fd /fs/erofs/zdata.c | |
parent | 8bb7eca972ad531c9b149c0a51ab43a417385813 (diff) | |
download | linux-86432a6dca9bed79111990851df5756d3eb5f57c.tar.bz2 |
erofs: fix unsafe pagevec reuse of hooked pclusters
There are pclusters in runtime marked with Z_EROFS_PCLUSTER_TAIL
before actual I/O submission. Thus, the decompression chain can be
extended if the following pcluster chain hooks such tail pcluster.
As the related comment mentioned, if some page is made of a hooked
pcluster and another followed pcluster, it can be reused for in-place
I/O (since I/O should be submitted anyway):
_______________________________________________________________
| tail (partial) page | head (partial) page |
|_____PRIMARY_HOOKED___|____________PRIMARY_FOLLOWED____________|
However, it's by no means safe to reuse as pagevec since if such
PRIMARY_HOOKED pclusters finally move into bypass chain without I/O
submission. It's somewhat hard to reproduce with LZ4 and I just found
it (general protection fault) by ro_fsstressing a LZMA image for long
time.
I'm going to actively clean up related code together with multi-page
folio adaption in the next few months. Let's address it directly for
easier backporting for now.
Call trace for reference:
z_erofs_decompress_pcluster+0x10a/0x8a0 [erofs]
z_erofs_decompress_queue.isra.36+0x3c/0x60 [erofs]
z_erofs_runqueue+0x5f3/0x840 [erofs]
z_erofs_readahead+0x1e8/0x320 [erofs]
read_pages+0x91/0x270
page_cache_ra_unbounded+0x18b/0x240
filemap_get_pages+0x10a/0x5f0
filemap_read+0xa9/0x330
new_sync_read+0x11b/0x1a0
vfs_read+0xf1/0x190
Link: https://lore.kernel.org/r/20211103182006.4040-1-xiang@kernel.org
Fixes: 3883a79abd02 ("staging: erofs: introduce VLE decompression support")
Cc: <stable@vger.kernel.org> # 4.19+
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Diffstat (limited to 'fs/erofs/zdata.c')
-rw-r--r-- | fs/erofs/zdata.c | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c index 11c7a1aaebad..eb51df4a9f77 100644 --- a/fs/erofs/zdata.c +++ b/fs/erofs/zdata.c @@ -373,8 +373,8 @@ static bool z_erofs_try_inplace_io(struct z_erofs_collector *clt, /* callers must be with collection lock held */ static int z_erofs_attach_page(struct z_erofs_collector *clt, - struct page *page, - enum z_erofs_page_type type) + struct page *page, enum z_erofs_page_type type, + bool pvec_safereuse) { int ret; @@ -384,9 +384,9 @@ static int z_erofs_attach_page(struct z_erofs_collector *clt, z_erofs_try_inplace_io(clt, page)) return 0; - ret = z_erofs_pagevec_enqueue(&clt->vector, page, type); + ret = z_erofs_pagevec_enqueue(&clt->vector, page, type, + pvec_safereuse); clt->cl->vcnt += (unsigned int)ret; - return ret ? 0 : -EAGAIN; } @@ -729,7 +729,8 @@ hitted: tight &= (clt->mode >= COLLECT_PRIMARY_FOLLOWED); retry: - err = z_erofs_attach_page(clt, page, page_type); + err = z_erofs_attach_page(clt, page, page_type, + clt->mode >= COLLECT_PRIMARY_FOLLOWED); /* should allocate an additional short-lived page for pagevec */ if (err == -EAGAIN) { struct page *const newpage = @@ -737,7 +738,7 @@ retry: set_page_private(newpage, Z_EROFS_SHORTLIVED_PAGE); err = z_erofs_attach_page(clt, newpage, - Z_EROFS_PAGE_TYPE_EXCLUSIVE); + Z_EROFS_PAGE_TYPE_EXCLUSIVE, true); if (!err) goto retry; } |