From: Gao Xiang hsiangkao@linux.alibaba.com
[ Upstream commit 94c43de73521d8ed7ebcfc6191d9dace1cbf7caa ]
When handling deduplicated compressed data, there can be multiple decompressed extents pointing to the same compressed data in one shot.
In such cases, the bvecs which belong to the longest extent will be selected as the primary bvecs for real decompressors to decode and the other duplicated bvecs will be directly copied from the primary bvecs.
Previously, only relative offsets of the longest extent were checked to decompress the primary bvecs. On rare occasions, it can be incorrect if there are several extents with the same start relative offset. As a result, some short bvecs could be selected for decompression and then cause data corruption.
For example, as Shijie Sun reported off-list, considering the following extents of a file: 117: 903345.. 915250 | 11905 : 385024.. 389120 | 4096 ... 119: 919729.. 930323 | 10594 : 385024.. 389120 | 4096 ... 124: 968881.. 980786 | 11905 : 385024.. 389120 | 4096
The start relative offset is the same: 2225, but extent 119 (919729.. 930323) is shorter than the others.
Let's restrict the bvec length in addition to the start offset if bvecs are not full.
Reported-by: Shijie Sun sunshijie@xiaomi.com Fixes: 5c2a64252c5d ("erofs: introduce partial-referenced pclusters") Tested-by Shijie Sun sunshijie@xiaomi.com Reviewed-by: Yue Hu huyue2@coolpad.com Reviewed-by: Chao Yu chao@kernel.org Signed-off-by: Gao Xiang hsiangkao@linux.alibaba.com Link: https://lore.kernel.org/r/20230719065459.60083-1-hsiangkao@linux.alibaba.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/erofs/zdata.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c index 533e612b6a486..361f3c29897e8 100644 --- a/fs/erofs/zdata.c +++ b/fs/erofs/zdata.c @@ -989,10 +989,11 @@ static void z_erofs_do_decompressed_bvec(struct z_erofs_decompress_backend *be, struct z_erofs_bvec *bvec) { struct z_erofs_bvec_item *item; + unsigned int pgnr;
- if (!((bvec->offset + be->pcl->pageofs_out) & ~PAGE_MASK)) { - unsigned int pgnr; - + if (!((bvec->offset + be->pcl->pageofs_out) & ~PAGE_MASK) && + (bvec->end == PAGE_SIZE || + bvec->offset + bvec->end == be->pcl->length)) { pgnr = (bvec->offset + be->pcl->pageofs_out) >> PAGE_SHIFT; DBG_BUGON(pgnr >= be->nr_pages); if (!be->decompressed_pages[pgnr]) {