[syzbot] [crypto?] KMSAN: uninit-value in sw842_compress (2)

[syzbot <syzbot+bf5586280a66e9ccdfa9@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    6f3ed7fec72f Merge tag 'for-7.1/dm-fixes-3' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17311750580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a0ca3b8cb3875012
dashboard link: https://syzkaller.appspot.com/bug?extid=bf5586280a66e9ccdfa9
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/74be992d336f/disk-6f3ed7fe.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d51c3e8d59b5/vmlinux-6f3ed7fe.xz
kernel image: https://storage.googleapis.com/syzbot-assets/34df0814d707/bzImage-6f3ed7fe.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bf5586280a66e9ccdfa9@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in sw842_compress+0xd09/0x5060 lib/842/842_compress.c:528
 sw842_compress+0xd09/0x5060 lib/842/842_compress.c:528
 crypto842_scompress+0x4e/0x70 crypto/842.c:46
 scomp_acomp_comp_decomp+0xa49/0x1120 include/crypto/internal/scompress.h:-1
 scomp_acomp_compress+0x33/0x40 crypto/scompress.c:280
 crypto_acomp_compress+0x5c4/0xe50 crypto/acompress.c:287
 zswap_compress mm/zswap.c:874 [inline]
 zswap_store_page mm/zswap.c:1415 [inline]
 zswap_store+0x1a1d/0x48b0 mm/zswap.c:1526
 swap_writeout+0x7a1/0x1120 mm/page_io.c:275
 shmem_writeout+0x1db1/0x2210 mm/shmem.c:1705
 writeout mm/vmscan.c:630 [inline]
 pageout mm/vmscan.c:679 [inline]
 shrink_folio_list+0x5ade/0x8000 mm/vmscan.c:1400
 evict_folios+0x9704/0xbb70 mm/vmscan.c:4854
 try_to_shrink_lruvec+0x1734/0x24b0 mm/vmscan.c:5009
 lru_gen_shrink_lruvec mm/vmscan.c:5173 [inline]
 shrink_lruvec+0x4f8/0x4e20 mm/vmscan.c:5932
 shrink_node_memcgs mm/vmscan.c:6171 [inline]
 shrink_node+0xf19/0x5a30 mm/vmscan.c:6215
 shrink_zones mm/vmscan.c:6454 [inline]
 do_try_to_free_pages+0x956/0x2640 mm/vmscan.c:6516
 try_to_free_mem_cgroup_pages+0x352/0x920 mm/vmscan.c:6838
 try_charge_memcg+0x815/0x1c20 mm/memcontrol.c:2627
 charge_memcg+0x113/0x410 mm/memcontrol.c:5021
 __mem_cgroup_charge+0x71/0x2e0 mm/memcontrol.c:5038
 mem_cgroup_charge include/linux/memcontrol.h:644 [inline]
 shmem_alloc_and_add_folio+0xe4d/0x1bd0 mm/shmem.c:1985
 shmem_get_folio_gfp+0xad3/0x1fc0 mm/shmem.c:2564
 shmem_get_folio mm/shmem.c:2670 [inline]
 shmem_write_begin+0x230/0x560 mm/shmem.c:3303
 generic_perform_write+0x364/0x1050 mm/filemap.c:4325
 shmem_file_write_iter+0x2b7/0x2f0 mm/shmem.c:3478
 __kernel_write_iter+0x6f9/0xdd0 fs/read_write.c:621
 dump_emit_page fs/coredump.c:1304 [inline]
 dump_user_range+0x1936/0x2070 fs/coredump.c:1378
 elf_core_dump+0x697e/0x6c30 fs/binfmt_elf.c:2109
 coredump_write+0x20c9/0x2ce0 fs/coredump.c:1053
 do_coredump fs/coredump.c:1132 [inline]
 vfs_coredump+0x7ae1/0x8f00 fs/coredump.c:1206
 get_signal+0x2075/0x29f0 kernel/signal.c:3022
 arch_do_signal_or_restart+0x53/0xc70 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:98 [inline]
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:244 [inline]
 irqentry_exit_to_user_mode include/linux/irq-entry-common.h:315 [inline]
 irqentry_exit+0x16f/0xa00 kernel/entry/common.c:162
 exc_page_fault+0x7e/0xb0 arch/x86/mm/fault.c:1530
 asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:618

Uninit was stored to memory at:
 memcpy_from_iter lib/iov_iter.c:85 [inline]
 iterate_bvec include/linux/iov_iter.h:123 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:306 [inline]
 iterate_and_advance include/linux/iov_iter.h:330 [inline]
 __copy_from_iter lib/iov_iter.c:261 [inline]
 copy_folio_from_iter_atomic+0xe91/0x3810 lib/iov_iter.c:491
 generic_perform_write+0x8b7/0x1050 mm/filemap.c:4343
 shmem_file_write_iter+0x2b7/0x2f0 mm/shmem.c:3478
 lo_rw_aio+0x1164/0x14a0 drivers/block/loop.c:-1
 do_req_filebacked drivers/block/loop.c:-1 [inline]
 loop_handle_cmd drivers/block/loop.c:1925 [inline]
 loop_process_work+0xf05/0x1ff0 drivers/block/loop.c:1960
 loop_workfn+0x3e/0x60 drivers/block/loop.c:1984
 process_one_work kernel/workqueue.c:3314 [inline]
 process_scheduled_works+0xb65/0x1e40 kernel/workqueue.c:3397
 worker_thread+0xee4/0x1590 kernel/workqueue.c:3478
 kthread+0x53a/0x5f0 kernel/kthread.c:436
 ret_from_fork+0x20f/0x8d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Uninit was created at:
 __alloc_frozen_pages_noprof+0x6fa/0x1000 mm/page_alloc.c:5244
 __alloc_pages_noprof mm/page_alloc.c:5255 [inline]
 alloc_pages_bulk_noprof+0x1664/0x1aa0 mm/page_alloc.c:5175
 btrfs_alloc_page_array fs/btrfs/extent_io.c:675 [inline]
 alloc_eb_folio_array fs/btrfs/extent_io.c:699 [inline]
 alloc_extent_buffer+0xa85/0x4670 fs/btrfs/extent_io.c:3495
 btrfs_find_create_tree_block+0x44/0x60 fs/btrfs/disk-io.c:574
 btrfs_init_new_buffer fs/btrfs/extent-tree.c:5260 [inline]
 btrfs_alloc_tree_block+0x3fe/0x1bc0 fs/btrfs/extent-tree.c:5373
 btrfs_alloc_log_tree_node fs/btrfs/disk-io.c:890 [inline]
 btrfs_add_log_tree+0x243/0x7a0 fs/btrfs/disk-io.c:938
 start_log_trans fs/btrfs/tree-log.c:349 [inline]
 btrfs_log_inode_parent+0x9cf/0x1e00 fs/btrfs/tree-log.c:7562
 btrfs_log_dentry_safe+0x96/0x130 fs/btrfs/tree-log.c:7668
 btrfs_sync_file+0x16bc/0x21c0 fs/btrfs/file.c:1736
 vfs_fsync_range+0x135/0x1c0 fs/sync.c:186
 generic_write_sync include/linux/fs.h:2654 [inline]
 btrfs_do_write_iter+0xb20/0xd70 fs/btrfs/file.c:1473
 btrfs_file_write_iter+0x38/0x50 fs/btrfs/file.c:1483
 do_iter_readv_writev+0x9e0/0xc10 fs/read_write.c:-1
 vfs_writev+0x52a/0x1500 fs/read_write.c:1059
 do_pwritev fs/read_write.c:1155 [inline]
 __do_sys_pwritev2 fs/read_write.c:1213 [inline]
 __se_sys_pwritev2+0x22f/0x470 fs/read_write.c:1204
 __x64_sys_pwritev2+0xe4/0x150 fs/read_write.c:1204
 x64_sys_call+0x10a2/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:329
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x15d/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 0 UID: 0 PID: 15366 Comm: syz.6.2383 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
=====================================================


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