linux-kernel - Re: [syzbot] [mm] KMSAN: uninit-value in sw842

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Message-ID: <68f9fb76.050a0220.346f24.0075.GAE@google.com>
Date: Thu, 23 Oct 2025 02:55:02 -0700
From: syzbot <syzbot+17cae3c0a5b0acdc327d@...kaller.appspotmail.com>
To: kubik.bartlomiej@...il.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [mm] KMSAN: uninit-value in sw842_compress

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KMSAN: uninit-value in sw842_decompress

=====================================================
BUG: KMSAN: uninit-value in crc32_be_base lib/crc/crc32-main.c:46 [inline]
BUG: KMSAN: uninit-value in crc32_be+0x215/0x270 lib/crc/crc32-main.c:80
 crc32_be_base lib/crc/crc32-main.c:46 [inline]
 crc32_be+0x215/0x270 lib/crc/crc32-main.c:80
 sw842_decompress+0x2223/0x23e0 lib/842/842_decompress.c:385
 crypto842_sdecompress+0x46/0x60 crypto/842.c:53
 scomp_acomp_comp_decomp+0xa49/0x1120 include/crypto/internal/scompress.h:-1
 scomp_acomp_decompress+0x30/0x40 crypto/scompress.c:287
 crypto_acomp_decompress+0x5b4/0xe80 crypto/acompress.c:303
 zswap_decompress+0x684/0xf40 mm/zswap.c:968
 zswap_load+0x262/0x570 mm/zswap.c:1628
 swap_read_folio+0x662/0x3050 mm/page_io.c:637
 swap_cluster_readahead+0xa8c/0xb20 mm/swap_state.c:672
 swapin_readahead+0x1d9/0x15b0 mm/swap_state.c:813
 do_swap_page+0xce9/0x9c40 mm/memory.c:4713
 handle_pte_fault mm/memory.c:6180 [inline]
 __handle_mm_fault mm/memory.c:6318 [inline]
 handle_mm_fault+0x4100/0xded0 mm/memory.c:6487
 do_user_addr_fault+0x1777/0x2550 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x74/0xc0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:618

Uninit was created at:
 __alloc_frozen_pages_noprof+0x689/0xf00 mm/page_alloc.c:5206
 alloc_pages_mpol+0x328/0x860 mm/mempolicy.c:2416
 folio_alloc_mpol_noprof+0x56/0x1d0 mm/mempolicy.c:2435
 __read_swap_cache_async+0x1f9/0x770 mm/swap_state.c:440
 swap_cluster_readahead+0xa0d/0xb20 mm/swap_state.c:669
 swapin_readahead+0x1d9/0x15b0 mm/swap_state.c:813
 do_swap_page+0xce9/0x9c40 mm/memory.c:4713
 handle_pte_fault mm/memory.c:6180 [inline]
 __handle_mm_fault mm/memory.c:6318 [inline]
 handle_mm_fault+0x4100/0xded0 mm/memory.c:6487
 do_user_addr_fault+0x1777/0x2550 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x74/0xc0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:618

CPU: 1 UID: 0 PID: 4809 Comm: dhcpcd Not tainted syzkaller #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
=====================================================


Tested on:

commit:         43e9ad0c Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=172213e2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=42e68cb86cfb456e
dashboard link: https://syzkaller.appspot.com/bug?extid=17cae3c0a5b0acdc327d
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=13b8b734580000