kernel/linux.git/fs/erofs, branch v6.12.101

erofs: fix use-after-free on sbi->sync_decompress

2026-06-19T11:42:18+00:00

[ Upstream commit 1aee05e814d292064bf5fa15733741040cdc48ba ] z_erofs_decompress_kickoff() can race with filesystem unmount, causing a use-after-free on sbi->sync_decompress. When I/O completes, z_erofs_endio() calls z_erofs_decompress_kickoff() to queue z_erofs_decompressqueue_work() asynchronously. Then, after all folios are unlocked, unmount workflow can proceed and sbi will be freed before accessing to sbi->sync_decompress. Thread (unmount) I/O completion kworker queue_work z_erofs_decompressqueue_work (all folios are unlocked) cleanup_mnt .. erofs_kill_sb erofs_sb_free kfree(sbi) access sbi->sync_decompress // UAF!! Fixes: 40452ffca3c1 ("erofs: add sysfs node to control sync decompression strategy") Reported-by: syzbot+52bae5c495dbe261a0bc@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=52bae5c495dbe261a0bc Reviewed-by: Chao Yu Reviewed-by: Jianan Huang Signed-off-by: Gao Xiang Signed-off-by: Sasha Levin

erofs: tidy up synchronous decompression

2026-06-19T11:42:18+00:00

[ Upstream commit cc831ab33644088c1eef78936de24701014d520a ] - Get rid of `sbi->opt.max_sync_decompress_pages` since it's fixed as 3 all the time; - Add Z_EROFS_MAX_SYNC_DECOMPRESS_BYTES in bytes instead of in pages, since for non-4K pages, 3-page limitation makes no sense; - Move `sync_decompress` to sbi to avoid unexpected remount impact; - Fold z_erofs_is_sync_decompress() into its caller; - Better description of sysfs entry `sync_decompress`. Reviewed-by: Chao Yu Signed-off-by: Gao Xiang Stable-dep-of: 1aee05e814d2 ("erofs: fix use-after-free on sbi->sync_decompress") Signed-off-by: Sasha Levin

erofs: add sysfs node to drop internal caches

2026-06-19T11:42:18+00:00

[ Upstream commit db80b98305f73ca83891e4228ead5f0324118b00 ] Add a sysfs node to drop compression-related caches, currently used to drop in-memory pclusters and cached compressed folios. Signed-off-by: Chunhai Guo Reviewed-by: Gao Xiang Link: https://lore.kernel.org/r/20241113041148.749129-1-guochunhai@vivo.com Signed-off-by: Gao Xiang Stable-dep-of: 1aee05e814d2 ("erofs: fix use-after-free on sbi->sync_decompress") Signed-off-by: Sasha Levin

erofs: unify lcn as u64 for 32-bit platforms

2026-05-23T11:04:47+00:00

[ Upstream commit 2d8c7edcb661812249469f4a5b62e9339118846f ] As sashiko reported [1], `lcn` was typed as `unsigned long` (or `unsigned int` sometimes), which is only 32 bits wide on 32-bit platforms, which causes `(lcn << lclusterbits)` to be truncated at 4 GiB. In order to consolidate the logic, just use `u64` consistently around the codebase. [1] https://sashiko.dev/r/20260420034612.1899973-1-hsiangkao%40linux.alibaba.com Fixes: 152a333a5895 ("staging: erofs: add compacted compression indexes support") Signed-off-by: Gao Xiang Signed-off-by: Sasha Levin

erofs: avoid infinite loops due to corrupted subpage compact indexes

2026-05-23T11:04:47+00:00

[ Upstream commit e13d315ae077bb7c3c6027cc292401bc0f4ec683 ] Robert reported an infinite loop observed by two crafted images. The root cause is that `clusterofs` can be larger than `lclustersize` for !NONHEAD `lclusters` in corrupted subpage compact indexes, e.g.: blocksize = lclustersize = 512 lcn = 6 clusterofs = 515 Move the corresponding check for full compress indexes to `z_erofs_load_lcluster_from_disk()` to also cover subpage compact compress indexes. It also fixes the position of `m->type >= Z_EROFS_LCLUSTER_TYPE_MAX` check, since it should be placed right after `z_erofs_load_{compact,full}_lcluster()`. Fixes: 8d2517aaeea3 ("erofs: fix up compacted indexes for block size < 4096") Fixes: 1a5223c182fd ("erofs: do sanity check on m->type in z_erofs_load_compact_lcluster()") Reported-by: Robert Morris Closes: https://lore.kernel.org/r/35167.1760645886@localhost Reviewed-by: Hongbo Li Signed-off-by: Gao Xiang Stable-dep-of: 2d8c7edcb661 ("erofs: unify lcn as u64 for 32-bit platforms") Signed-off-by: Sasha Levin

erofs: do sanity check on m->type in z_erofs_load_compact_lcluster()

2026-05-23T11:04:47+00:00

[ Upstream commit 1a5223c182fdb3bb3c0ca85cec101c740f685ab6 ] All below functions will do sanity check on m->type, let's move sanity check to z_erofs_load_compact_lcluster() for cleanup. - z_erofs_map_blocks_fo - z_erofs_get_extent_compressedlen - z_erofs_get_extent_decompressedlen - z_erofs_extent_lookback Reviewed-by: Hongbo Li Signed-off-by: Chao Yu Reviewed-by: Gao Xiang Link: https://lore.kernel.org/r/20250708110928.3110375-1-chao@kernel.org Signed-off-by: Gao Xiang Stable-dep-of: 2d8c7edcb661 ("erofs: unify lcn as u64 for 32-bit platforms") Signed-off-by: Sasha Levin

erofs: add encoded extent on-disk definition

2026-05-23T11:04:46+00:00

[ Upstream commit efb2aef569b35b415c232c4e9fdecd0e540e1f60 ] Previously, EROFS provided both (non-)compact compressed indexes to keep necessary hints for each logical block, enabling O(1) random indexing. This approach was originally designed for small compression units (e.g., 4KiB), where compressed data is strictly block-aligned via fixed-sized output compression. However, EROFS now supports big pclusters up to 1MiB and many users use large configurations to minimize image sizes. For such configurations, the total number of extents decreases significantly (e.g., only 1,024 extents for a 1GiB file using 1MiB pclusters), then runtime metadata overhead becomes negligible compared to data I/O and decoding costs. Additionally, some popular compression algorithm (mainly Zstd) still lacks native fixed-sized output compression support (although it's planned by their authors). Instead of just waiting for compressor improvements, let's adopt byte-oriented extents, allowing these compressors to retain their current methods. For example, it speeds up Zstd compression a lot: Processor: Intel(R) Xeon(R) Platinum 8163 CPU @ 2.50GHz * 96 Dataset: enwik9 Build time Size Type Command Line 3m52.339s 266653696 FO -C524288 -zzstd,22 3m48.549s 266174464 FO -E48bit -C524288 -zzstd,22 0m12.821s 272134144 FI -E48bit -C1048576 --max-extent-bytes=1048576 -zzstd,22 0m14.528s 248987648 FO -C1048576 -zlzma,9 0m14.605s 248504320 FO -E48bit -C1048576 -zlzma,9 Encoded extents are structured as an array of `struct z_erofs_extent`, sorted by logical address in ascending order: __le32 plen // encoded length, algorithm id and flags __le32 pstart_lo // physical offset LSB __le32 pstart_hi // physical offset MSB __le32 lstart_lo // logical offset __le32 lstart_hi // logical offset MSB .. Note that prefixed reduced records can be used to minimize metadata for specific cases (e.g. lstart less than 32 bits, then 32 to 16 bytes). If the logical lengths of all encoded extents are the same, 4-byte (plen) and 8-byte (plen, pstart_lo) records can be used. Or, 16-byte (plen .. lstart_lo) and 32-byte full records have to be used instead. If 16-byte and 32-byte records are used, the total number of extents is kept in `struct z_erofs_map_header`, and binary search can be applied on them. Note that `eytzinger order` is not considerd because data sequential access is important. If 4-byte records are used, 8-byte start physical offset is between `struct z_erofs_map_header` and the `plen` array. In addition, 64-bit physical offsets can be applied with new encoded extent format to match full 48-bit block addressing. Remove redundant comments around `struct z_erofs_lcluster_index` too. Signed-off-by: Gao Xiang Acked-by: Chao Yu Link: https://lore.kernel.org/r/20250310095459.2620647-8-hsiangkao@linux.alibaba.com Stable-dep-of: 2d8c7edcb661 ("erofs: unify lcn as u64 for 32-bit platforms") Signed-off-by: Sasha Levin

erofs: fix unsigned underflow in z_erofs_lz4_handle_overlap()

2026-05-14T13:29:29+00:00

[ Upstream commit 21e161de2dc660b1bb70ef5b156ab8e6e1cca3ab ] Some crafted images can have illegal (!partial_decoding && m_llen < m_plen) extents, and the LZ4 inplace decompression path can be wrongly hit, but it cannot handle (outpages < inpages) properly: "outpages - inpages" wraps to a large value and the subsequent rq->out[] access reads past the decompressed_pages array. However, such crafted cases can correctly result in a corruption report in the normal LZ4 non-inplace path. Let's add an additional check to fix this for backporting. Reproducible image (base64-encoded gzipped blob): H4sIAJGR12kCA+3SPUoDQRgG4MkmkkZk8QRbRFIIi9hbpEjrHQI5ghfwCN5BLCzTGtLbBI+g dilSJo1CnIm7GEXFxhT6PDDwfrs73/ywIQD/1ePD4r7Ou6ETsrq4mu7XcWfj++Pb58nJU/9i PNtbjhan04/9GtX4qVYc814WDqt6FaX5s+ZwXXeq52lndT6IuVvlblytLMvh4Gzwaf90nsvz 2DF/21+20T/ldgp5s1jXRaN4t/8izsy/OUB6e/Qa79r+JwAAAAAAAL52vQVuGQAAAP6+my1w ywAAAAAAAADwu14ATsEYtgBQAAA= $ mount -t erofs -o cache_strategy=disabled foo.erofs /mnt $ dd if=/mnt/data of=/dev/null bs=4096 count=1 Fixes: 598162d05080 ("erofs: support decompress big pcluster for lz4 backend") Reported-by: Yuhao Jiang Cc: stable@vger.kernel.org Signed-off-by: Junrui Luo Reviewed-by: Gao Xiang Signed-off-by: Gao Xiang Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

erofs: tidy up z_erofs_lz4_handle_overlap()

2026-05-14T13:29:28+00:00

[ Upstream commit 9ae77198d4815c63fc8ebacc659c71d150d1e51b ] - Add some useful comments to explain inplace I/Os and decompression; - Rearrange the code to get rid of one unnecessary goto. Reviewed-by: Chao Yu Signed-off-by: Gao Xiang Stable-dep-of: 21e161de2dc6 ("erofs: fix unsigned underflow in z_erofs_lz4_handle_overlap()") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

erofs: move {in,out}pages into struct z_erofs_decompress_req

2026-05-14T13:29:28+00:00

[ Upstream commit 0243cc257ffa6d8cb210a3070b687fb510f113c7 ] It seems that all compressors need those two values, so just move them into the common structure. `struct z_erofs_lz4_decompress_ctx` can be dropped too. Reviewed-by: Chao Yu Signed-off-by: Gao Xiang Link: https://lore.kernel.org/r/20250305124007.1810731-1-hsiangkao@linux.alibaba.com Stable-dep-of: 21e161de2dc6 ("erofs: fix unsigned underflow in z_erofs_lz4_handle_overlap()") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman