kernel/linux.git/fs/erofs, branch v6.12.80

erofs: add GFP_NOIO in the bio completion if needed

2026-04-02T11:09:43+00:00

commit c23df30915f83e7257c8625b690a1cece94142a0 upstream. The bio completion path in the process context (e.g. dm-verity) will directly call into decompression rather than trigger another workqueue context for minimal scheduling latencies, which can then call vm_map_ram() with GFP_KERNEL. Due to insufficient memory, vm_map_ram() may generate memory swapping I/O, which can cause submit_bio_wait to deadlock in some scenarios. Trimmed down the call stack, as follows: f2fs_submit_read_io submit_bio //bio_list is initialized. mmc_blk_mq_recovery z_erofs_endio vm_map_ram __pte_alloc_kernel __alloc_pages_direct_reclaim shrink_folio_list __swap_writepage submit_bio_wait //bio_list is non-NULL, hang!!! Use memalloc_noio_{save,restore}() to wrap up this path. Reviewed-by: Gao Xiang Signed-off-by: Jiucheng Xu Reviewed-by: Chao Yu Signed-off-by: Gao Xiang Signed-off-by: Greg Kroah-Hartman

erofs: set fileio bio failed in short read case

2026-04-02T11:09:31+00:00

[ Upstream commit eade54040384f54b7fb330e4b0975c5734850b3c ] For file-backed mount, IO requests are handled by vfs_iocb_iter_read(). However, it can be interrupted by SIGKILL, returning the number of bytes actually copied. Unused folios in bio are unexpectedly marked as uptodate. vfs_read filemap_read filemap_get_pages filemap_readahead erofs_fileio_readahead erofs_fileio_rq_submit vfs_iocb_iter_read filemap_read filemap_get_pages <= detect signal erofs_fileio_ki_complete <= set all folios uptodate This patch addresses this by setting short read bio with an error directly. Fixes: bc804a8d7e86 ("erofs: handle end of filesystem properly for file-backed mounts") Reported-by: chenguanyou Signed-off-by: Yunlei He Signed-off-by: Sheng Yong Reviewed-by: Gao Xiang Reviewed-by: Chao Yu Signed-off-by: Gao Xiang Signed-off-by: Sasha Levin

erofs: fix inline data read failure for ztailpacking pclusters

2026-03-25T10:08:45+00:00

[ Upstream commit c134a40f86efb8d6b5a949ef70e06d5752209be5 ] Compressed folios for ztailpacking pclusters must be valid before adding these pclusters to I/O chains. Otherwise, z_erofs_decompress_pcluster() may assume they are already valid and then trigger a NULL pointer dereference. It is somewhat hard to reproduce because the inline data is in the same block as the tail of the compressed indexes, which are usually read just before. However, it may still happen if a fatal signal arrives while read_mapping_folio() is running, as shown below: erofs: (device dm-1): z_erofs_pcluster_begin: failed to get inline data -4 Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008 ... pc : z_erofs_decompress_queue+0x4c8/0xa14 lr : z_erofs_decompress_queue+0x160/0xa14 sp : ffffffc08b3eb3a0 x29: ffffffc08b3eb570 x28: ffffffc08b3eb418 x27: 0000000000001000 x26: ffffff8086ebdbb8 x25: ffffff8086ebdbb8 x24: 0000000000000001 x23: 0000000000000008 x22: 00000000fffffffb x21: dead000000000700 x20: 00000000000015e7 x19: ffffff808babb400 x18: ffffffc089edc098 x17: 00000000c006287d x16: 00000000c006287d x15: 0000000000000004 x14: ffffff80ba8f8000 x13: 0000000000000004 x12: 00000006589a77c9 x11: 0000000000000015 x10: 0000000000000000 x9 : 0000000000000000 x8 : 0000000000000000 x7 : 0000000000000000 x6 : 000000000000003f x5 : 0000000000000040 x4 : ffffffffffffffe0 x3 : 0000000000000020 x2 : 0000000000000008 x1 : 0000000000000000 x0 : 0000000000000000 Call trace: z_erofs_decompress_queue+0x4c8/0xa14 z_erofs_runqueue+0x908/0x97c z_erofs_read_folio+0x128/0x228 filemap_read_folio+0x68/0x128 filemap_get_pages+0x44c/0x8b4 filemap_read+0x12c/0x5b8 generic_file_read_iter+0x4c/0x15c do_iter_readv_writev+0x188/0x1e0 vfs_iter_read+0xac/0x1a4 backing_file_read_iter+0x170/0x34c ovl_read_iter+0xf0/0x140 vfs_read+0x28c/0x344 ksys_read+0x80/0xf0 __arm64_sys_read+0x24/0x34 invoke_syscall+0x60/0x114 el0_svc_common+0x88/0xe4 do_el0_svc+0x24/0x30 el0_svc+0x40/0xa8 el0t_64_sync_handler+0x70/0xbc el0t_64_sync+0x1bc/0x1c0 Fix this by reading the inline data before allocating and adding the pclusters to the I/O chains. Fixes: cecf864d3d76 ("erofs: support inline data decompression") Reported-by: Zhiguo Niu Reviewed-and-tested-by: Zhiguo Niu Signed-off-by: Gao Xiang Signed-off-by: Zhiguo Niu Signed-off-by: Greg Kroah-Hartman

erofs: handle end of filesystem properly for file-backed mounts

2026-03-04T12:19:25+00:00

[ Upstream commit bc804a8d7e865ef47fb7edcaf5e77d18bf444ebc ] I/O requests beyond the end of the filesystem should be zeroed out, similar to loopback devices and that is what we expect. Fixes: ce63cb62d794 ("erofs: support unencoded inodes for fileio") Signed-off-by: Gao Xiang Signed-off-by: Sasha Levin

erofs: get rid of raw bi_end_io() usage

2026-03-04T12:19:25+00:00

[ Upstream commit 80d0c27a0a4af8e0678d7412781482e6f73c22c7 ] These BIOs are actually harmless in practice, as they are all pseudo BIOs and do not use advanced features like chaining. Using the BIO interface is a more friendly and unified approach for both bdev and and file-backed I/Os (compared to awkward bvec interfaces). Let's use bio_endio() instead. Reviewed-by: Christoph Hellwig Reviewed-by: Ming Lei Reviewed-by: Chao Yu Signed-off-by: Gao Xiang Stable-dep-of: bc804a8d7e86 ("erofs: handle end of filesystem properly for file-backed mounts") Signed-off-by: Sasha Levin

erofs: fix UAF issue for file-backed mounts w/ directio option

2026-02-16T09:18:45+00:00

commit 1caf50ce4af096d0280d59a31abdd85703cd995c upstream. [ 9.269940][ T3222] Call trace: [ 9.269948][ T3222] ext4_file_read_iter+0xac/0x108 [ 9.269979][ T3222] vfs_iocb_iter_read+0xac/0x198 [ 9.269993][ T3222] erofs_fileio_rq_submit+0x12c/0x180 [ 9.270008][ T3222] erofs_fileio_submit_bio+0x14/0x24 [ 9.270030][ T3222] z_erofs_runqueue+0x834/0x8ac [ 9.270054][ T3222] z_erofs_read_folio+0x120/0x220 [ 9.270083][ T3222] filemap_read_folio+0x60/0x120 [ 9.270102][ T3222] filemap_fault+0xcac/0x1060 [ 9.270119][ T3222] do_pte_missing+0x2d8/0x1554 [ 9.270131][ T3222] handle_mm_fault+0x5ec/0x70c [ 9.270142][ T3222] do_page_fault+0x178/0x88c [ 9.270167][ T3222] do_translation_fault+0x38/0x54 [ 9.270183][ T3222] do_mem_abort+0x54/0xac [ 9.270208][ T3222] el0_da+0x44/0x7c [ 9.270227][ T3222] el0t_64_sync_handler+0x5c/0xf4 [ 9.270253][ T3222] el0t_64_sync+0x1bc/0x1c0 EROFS may encounter above panic when enabling file-backed mount w/ directio mount option, the root cause is it may suffer UAF in below race condition: - z_erofs_read_folio wq s_dio_done_wq - z_erofs_runqueue - erofs_fileio_submit_bio - erofs_fileio_rq_submit - vfs_iocb_iter_read - ext4_file_read_iter - ext4_dio_read_iter - iomap_dio_rw : bio was submitted and return -EIOCBQUEUED - dio_aio_complete_work - dio_complete - dio->iocb->ki_complete (erofs_fileio_ki_complete()) - kfree(rq) : it frees iocb, iocb.ki_filp can be UAF in file_accessed(). - file_accessed : access NULL file point Introduce a reference count in struct erofs_fileio_rq, and initialize it as two, both erofs_fileio_ki_complete() and erofs_fileio_rq_submit() will decrease reference count, the last one decreasing the reference count to zero will free rq. Cc: stable@kernel.org Fixes: fb176750266a ("erofs: add file-backed mount support") Fixes: 6422cde1b0d5 ("erofs: use buffered I/O for file-backed mounts by default") Signed-off-by: Chao Yu Reviewed-by: Gao Xiang Signed-off-by: Gao Xiang Signed-off-by: Greg Kroah-Hartman

erofs: fix file-backed mounts no longer working on EROFS partitions

2026-01-17T15:31:25+00:00

[ Upstream commit 7893cc12251f6f19e7689a4cf3ba803bddbd8437 ] Sheng Yong reported [1] that Android APEX images didn't work with commit 072a7c7cdbea ("erofs: don't bother with s_stack_depth increasing for now") because "EROFS-formatted APEX file images can be stored within an EROFS-formatted Android system partition." In response, I sent a quick fat-fingered [PATCH v3] to address the report. Unfortunately, the updated condition was incorrect: if (erofs_is_fileio_mode(sbi)) { - sb->s_stack_depth = - file_inode(sbi->dif0.file)->i_sb->s_stack_depth + 1; - if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) { - erofs_err(sb, "maximum fs stacking depth exceeded"); + inode = file_inode(sbi->dif0.file); + if ((inode->i_sb->s_op == &erofs_sops && !sb->s_bdev) || + inode->i_sb->s_stack_depth) { The condition `!sb->s_bdev` is always true for all file-backed EROFS mounts, making the check effectively a no-op. The real fix tested and confirmed by Sheng Yong [2] at that time was [PATCH v3 RESEND], which correctly ensures the following EROFS^2 setup works: EROFS (on a block device) + EROFS (file-backed mount) But sadly I screwed it up again by upstreaming the outdated [PATCH v3]. This patch applies the same logic as the delta between the upstream [PATCH v3] and the real fix [PATCH v3 RESEND]. Reported-by: Sheng Yong Closes: https://lore.kernel.org/r/3acec686-4020-4609-aee4-5dae7b9b0093@gmail.com [1] Fixes: 072a7c7cdbea ("erofs: don't bother with s_stack_depth increasing for now") Link: https://lore.kernel.org/r/243f57b8-246f-47e7-9fb1-27a771e8e9e8@gmail.com [2] Signed-off-by: Gao Xiang Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

erofs: don't bother with s_stack_depth increasing for now

2026-01-17T15:31:25+00:00

[ Upstream commit 072a7c7cdbea4f91df854ee2bb216256cd619f2a ] Previously, commit d53cd891f0e4 ("erofs: limit the level of fs stacking for file-backed mounts") bumped `s_stack_depth` by one to avoid kernel stack overflow when stacking an unlimited number of EROFS on top of each other. This fix breaks composefs mounts, which need EROFS+ovl^2 sometimes (and such setups are already used in production for quite a long time). One way to fix this regression is to bump FILESYSTEM_MAX_STACK_DEPTH from 2 to 3, but proving that this is safe in general is a high bar. After a long discussion on GitHub issues [1] about possible solutions, one conclusion is that there is no need to support nesting file-backed EROFS mounts on stacked filesystems, because there is always the option to use loopback devices as a fallback. As a quick fix for the composefs regression for this cycle, instead of bumping `s_stack_depth` for file backed EROFS mounts, we disallow nesting file-backed EROFS over EROFS and over filesystems with `s_stack_depth` > 0. This works for all known file-backed mount use cases (composefs, containerd, and Android APEX for some Android vendors), and the fix is self-contained. Essentially, we are allowing one extra unaccounted fs stacking level of EROFS below stacking filesystems, but EROFS can only be used in the read path (i.e. overlayfs lower layers), which typically has much lower stack usage than the write path. We can consider increasing FILESYSTEM_MAX_STACK_DEPTH later, after more stack usage analysis or using alternative approaches, such as splitting the `s_stack_depth` limitation according to different combinations of stacking. Fixes: d53cd891f0e4 ("erofs: limit the level of fs stacking for file-backed mounts") Reported-and-tested-by: Dusty Mabe Reported-by: Timothée Ravier Closes: https://github.com/coreos/fedora-coreos-tracker/issues/2087 [1] Reported-by: "Alekséi Naidénov" Closes: https://lore.kernel.org/r/CAFHtUiYv4+=+JP_-JjARWjo6OwcvBj1wtYN=z0QXwCpec9sXtg@mail.gmail.com Acked-by: Amir Goldstein Acked-by: Alexander Larsson Reviewed-and-tested-by: Sheng Yong Reviewed-by: Zhiguo Niu Reviewed-by: Chao Yu Cc: Christian Brauner Cc: Miklos Szeredi Signed-off-by: Gao Xiang Signed-off-by: Sasha Levin

erofs: fix unexpected EIO under memory pressure

2026-01-08T09:14:56+00:00

[ Upstream commit 4012d78562193ef5eb613bad4b0c0fa187637cfe ] erofs readahead could fail with ENOMEM under the memory pressure because it tries to alloc_page with GFP_NOWAIT | GFP_NORETRY, while GFP_KERNEL for a regular read. And if readahead fails (with non-uptodate folios), the original request will then fall back to synchronous read, and `.read_folio()` should return appropriate errnos. However, in scenarios where readahead and read operations compete, read operation could return an unintended EIO because of an incorrect error propagation. To resolve this, this patch modifies the behavior so that, when the PCL is for read(which means pcl.besteffort is true), it attempts actual decompression instead of propagating the privios error except initial EIO. - Page size: 4K - The original size of FileA: 16K - Compress-ratio per PCL: 50% (Uncompressed 8K -> Compressed 4K) [page0, page1] [page2, page3] [PCL0]---------[PCL1] - functions declaration: . pread(fd, buf, count, offset) . readahead(fd, offset, count) - Thread A tries to read the last 4K - Thread B tries to do readahead 8K from 4K - RA, besteffort == false - R, besteffort == true pread(FileA, buf, 4K, 12K) do readahead(page3) // failed with ENOMEM wait_lock(page3) if (!uptodate(page3)) goto do_read readahead(FileA, 4K, 8K) // Here create PCL-chain like below: // [null, page1] [page2, null] // [PCL0:RA]-----[PCL1:RA] ... do read(page3) // found [PCL1:RA] and add page3 into it, // and then, change PCL1 from RA to R ... // Now, PCL-chain is as below: // [null, page1] [page2, page3] // [PCL0:RA]-----[PCL1:R] // try to decompress PCL-chain... z_erofs_decompress_queue err = 0; // failed with ENOMEM, so page 1 // only for RA will not be uptodated. // it's okay. err = decompress([PCL0:RA], err) // However, ENOMEM propagated to next // PCL, even though PCL is not only // for RA but also for R. As a result, // it just failed with ENOMEM without // trying any decompression, so page2 // and page3 will not be uptodated. ** BUG HERE ** --> err = decompress([PCL1:R], err) return err as ENOMEM ... wait_lock(page3) if (!uptodate(page3)) return EIO <-- Return an unexpected EIO! ... Fixes: 2349d2fa02db ("erofs: sunset unneeded NOFAILs") Cc: stable@vger.kernel.org Reviewed-by: Jaewook Kim Reviewed-by: Sungjong Seo Signed-off-by: Junbeom Yeom Reviewed-by: Gao Xiang Signed-off-by: Gao Xiang [ Adjust context ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

erofs: limit the level of fs stacking for file-backed mounts

2025-12-18T12:55:05+00:00

[ Upstream commit d53cd891f0e4311889349fff3a784dc552f814b9 ] Otherwise, it could cause potential kernel stack overflow (e.g., EROFS mounting itself). Reviewed-by: Sheng Yong Fixes: fb176750266a ("erofs: add file-backed mount support") Reviewed-by: Chao Yu Reviewed-by: Hongbo Li Signed-off-by: Gao Xiang Signed-off-by: Sasha Levin