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
[ Upstream commit 35076d2223c731f7be75af61e67f90807384d030 ]
When compressed data deduplication is enabled, multiple logical extents may reference the same compressed physical cluster.
The previous commit 94c43de73521 ("erofs: fix wrong primary bvec selection on deduplicated extents") already avoids using shortened bvecs. However, in such cases, the extra temporary buffers also need to be preserved for later use in z_erofs_fill_other_copies() to to prevent data corruption.
IOWs, extra temporary buffers have to be retained not only due to varying start relative offsets (`pageofs_out`, as indicated by `pcl->multibases`) but also because of shortened bvecs.
android.hardware.graphics.composer@2.1.so : 270696 bytes 0: 0.. 204185 | 204185 : 628019200.. 628084736 | 65536 -> 1: 204185.. 225536 | 21351 : 544063488.. 544129024 | 65536 2: 225536.. 270696 | 45160 : 0.. 0 | 0
com.android.vndk.v28.apex : 93814897 bytes ... 364: 53869896..54095257 | 225361 : 543997952.. 544063488 | 65536 -> 365: 54095257..54309344 | 214087 : 544063488.. 544129024 | 65536 366: 54309344..54514557 | 205213 : 544129024.. 544194560 | 65536 ...
Both 204185 and 54095257 have the same start relative offset of 3481, but the logical page 55 of `android.hardware.graphics.composer@2.1.so` ranges from 225280 to 229632, forming a shortened bvec [225280, 225536) that cannot be used for decompressing the range from 54095257 to 54309344 of `com.android.vndk.v28.apex`.
Since `pcl->multibases` is already meaningless, just mark `be->keepxcpy` on demand for simplicity.
Again, this issue can only lead to data corruption if `-Ededupe` is on.
Fixes: 94c43de73521 ("erofs: fix wrong primary bvec selection on deduplicated extents") Reviewed-by: Hongbo Li lihongbo22@huawei.com Signed-off-by: Gao Xiang hsiangkao@linux.alibaba.com Link: https://lore.kernel.org/r/20250506101850.191506-1-hsiangkao@linux.alibaba.co... Signed-off-by: Sasha Levin sashal@kernel.org --- fs/erofs/zdata.c | 31 ++++++++++++++----------------- 1 file changed, 14 insertions(+), 17 deletions(-)
diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c index a8fb4b525f544..e5e94afc5af88 100644 --- a/fs/erofs/zdata.c +++ b/fs/erofs/zdata.c @@ -82,9 +82,6 @@ struct z_erofs_pcluster { /* L: whether partial decompression or not */ bool partial;
- /* L: indicate several pageofs_outs or not */ - bool multibases; - /* L: whether extra buffer allocations are best-effort */ bool besteffort;
@@ -1073,8 +1070,6 @@ static int z_erofs_scan_folio(struct z_erofs_decompress_frontend *f, break;
erofs_onlinefolio_split(folio); - if (f->pcl->pageofs_out != (map->m_la & ~PAGE_MASK)) - f->pcl->multibases = true; if (f->pcl->length < offset + end - map->m_la) { f->pcl->length = offset + end - map->m_la; f->pcl->pageofs_out = map->m_la & ~PAGE_MASK; @@ -1120,7 +1115,6 @@ struct z_erofs_decompress_backend { struct page *onstack_pages[Z_EROFS_ONSTACK_PAGES]; struct super_block *sb; struct z_erofs_pcluster *pcl; - /* pages with the longest decompressed length for deduplication */ struct page **decompressed_pages; /* pages to keep the compressed data */ @@ -1129,6 +1123,8 @@ struct z_erofs_decompress_backend { struct list_head decompressed_secondary_bvecs; struct page **pagepool; unsigned int onstack_used, nr_pages; + /* indicate if temporary copies should be preserved for later use */ + bool keepxcpy; };
struct z_erofs_bvec_item { @@ -1139,18 +1135,20 @@ struct z_erofs_bvec_item { static void z_erofs_do_decompressed_bvec(struct z_erofs_decompress_backend *be, struct z_erofs_bvec *bvec) { + int poff = bvec->offset + be->pcl->pageofs_out; struct z_erofs_bvec_item *item; - 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]) { - be->decompressed_pages[pgnr] = bvec->page; + struct page **page; + + if (!(poff & ~PAGE_MASK) && (bvec->end == PAGE_SIZE || + bvec->offset + bvec->end == be->pcl->length)) { + DBG_BUGON((poff >> PAGE_SHIFT) >= be->nr_pages); + page = be->decompressed_pages + (poff >> PAGE_SHIFT); + if (!*page) { + *page = bvec->page; return; } + } else { + be->keepxcpy = true; }
/* (cold path) one pcluster is requested multiple times */ @@ -1316,7 +1314,7 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be, .alg = pcl->algorithmformat, .inplace_io = overlapped, .partial_decoding = pcl->partial, - .fillgaps = pcl->multibases, + .fillgaps = be->keepxcpy, .gfp = pcl->besteffort ? GFP_KERNEL : GFP_NOWAIT | __GFP_NORETRY }, be->pagepool); @@ -1370,7 +1368,6 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
pcl->length = 0; pcl->partial = true; - pcl->multibases = false; pcl->besteffort = false; pcl->bvset.nextpage = NULL; pcl->vcnt = 0;