From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 974C7367292 for ; Fri, 25 Sep 2026 18:55:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790362537; cv=none; b=mixZ6P0Jl5P7cQ62ytYI0W9fM5KkhswUatxjWZlWdzNql6vjr5a2bF/4Oc7WY0WQBdHSSiG/dRksvaoqX2AXNayxSzDRaIVm5XytQYQ95YtmD8mpaaxZJFvyVOMKUdobL31iR5Cr6ueR+nTgKDFcasFBq+Ma/x6H5fEE8kBl854= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790362537; c=relaxed/simple; bh=tZyxKV8byy4rK4nsrt3qWyIBK1kglTEypt2on/tYro4=; h=From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type:Date; b=uZNqIaKXAyro8/uudwddojMGIiN/2VVrnVfEjqROOEiXsoZjeLz1Ne6xZPoTDQfVgEvHSee24Jdj+3bTvzY6ks4csrhGxZ5dsVrkNKPETURCclwFTEKyNMOF7FyxWGJAD5725Ws+pMMbxenBJH4q4HfqUKBUYwhwBmIJ/vvm0us= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cs+m6h9/; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="cs+m6h9/" Received: by smtp.kernel.org (Postfix) with UTF8SMTPSA id 039BB1F000FF; Fri, 25 Sep 2026 18:55:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790362536; bh=4sYRB6Gl0aFeKDBKZUtK/AGzYkz3JxI98xTlQpmlQ6M=; h=From:To:Cc:Subject:Date; b=cs+m6h9/jPfZBZQtnFd6caPhYDFI4AuLEVVflinqimasy0N8GUDtX7OaSTYthHBJx hS6o5U69qjYcheWqD+JWWVbrgQ5L/POxLVNM0WEsrarZ1eIQPn+SfVCzlbF2tweitR tpy62iZir6rumWds9aEga7G14n+dk1Juzxu/REUev0O/XA0hh4VrfkZBceZiTgBKbE gvx2WIdBqTsuBURwPwK6bPnwPeFUAbQWni3t4uvcxMTdDyo65xeWTXSvBu/iqYnzHO Qf+4jfPuVxokEb+exxDkDn9avh3mdjpPK1ql/4vg6Dz6ANK53jbsa9COATrOAu4Z6y kpVtX7I+qCdQw== From: "syzbot" To: syzkaller-upstream-moderation@googlegroups.com Cc: immersa.bartosz.chronowski@gmail.com, syzbot@lists.linux.dev Subject: [PATCH RFC v7] jfs: validate dmap start before block allocation Message-ID: Precedence: bulk X-Mailing-List: syzbot@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Date: Fri, 25 Sep 2026 18:55:35 +0000 (UTC) A corrupted JFS filesystem image can cause a state where the block allocation map (bmap) and the dmap pages are out of sync. Specifically, dbAllocNear() and dbAllocDmapLev() derive the returned block number from on-disk dp->start, which can cause duplicate allocation if dp->start does not match the selected dmap boundary. In this scenario, the allocator returns a block number that is already in use (e.g., as an inode table block or metadata) while marking a completely different block as allocated. When a thread later attempts to lock this duplicate block (for example, during a directory btree split), txLock() detects a metapage conflict because the block is already locked for another purpose, triggering a kernel BUG: kernel BUG at fs/jfs/jfs_txnmgr.c:836! Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI RIP: 0010:txLock+0x1cc3/0x1d10 fs/jfs/jfs_txnmgr.c:836 Call Trace: dtSplitRoot+0x38d/0x18a0 fs/jfs/jfs_dtree.c:1924 dtSplitUp fs/jfs/jfs_dtree.c:990 [inline] dtInsert+0xeb2/0x5890 fs/jfs/jfs_dtree.c:868 jfs_create+0x730/0xae0 fs/jfs/namei.c:138 ... Validation of dp->start against the expected dmap boundary in dbAlloc() and the single-dmap path of dbAllocCtl() prevents inconsistent allocation. Rejecting a mismatched start with -EIO prevents duplicate allocations before txLock() is reached. Additionally, preserve the existing independent geometry check (dp->tree.budmin < 0) in dbAllocCtl(). Both a mismatched start and a negative budmin will now fail with -EIO early, preventing corrupted dmap structures from causing duplicate allocations and subsequent transaction lock crashes. Assisted-by: Gemini:gemini-3.8-flash syzbot Reported-by: syzbot+a843f6ae2130a987d63b@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=a843f6ae2130a987d63b Link: https://syzkaller.appspot.com/ai_job?id=922ceb61-4be2-4af9-b2fe-9977a2549134 To: To: "Dave Kleikamp" Cc: "Kees Cook" Cc: Cc: "Yun Zhou" --- v7: - Update commit description to explain that dbAllocNear() and dbAllocDmapLev() derive the returned block number from on-disk dp->start and clarify the validation in dbAlloc() and dbAllocCtl(). v6: - Dropped Linus Torvalds from the To/Cc list. https://lore.kernel.org/all/a8ef6423-9a58-4396-a030-92690f02f44c@mail.kernel.org/T/ v5: - Narrowed the validation of `dp->start` to only the primary block allocation paths (`dbAlloc` and `dbAllocCtl`). - Removed validation checks from `dbFree`, `dbUpdatePMap`, `dbExtend`, `dbAllocBottomUp`, and secondary loops in `dbAllocCtl`. https://lore.kernel.org/all/6673d9d2-210e-4870-b355-7826289ab842@mail.kernel.org/T/ v4: - Renamed dbValidateDmap to db_validate_dmap to follow kernel naming conventions. - Preserved the existing dp->tree.budmin < 0 check in dbAllocCtl instead of replacing it. https://lore.kernel.org/all/d1405703-afc9-40f9-bc57-ddedf66f35da@mail.kernel.org/T/ v3: - Renamed the patch to "jfs: validate dmap start before block map operations". - Simplified dbValidateDmap() to only validate that the dmap dp->start matches the expected start block number, removing unproven integrity checks. - Updated the commit description to explain the exact root cause of the selection/update mismatch and how validating dp->start prevents duplicate allocations before txLock() is reached. https://lore.kernel.org/all/7c3c4fb4-ccbd-486f-b087-6074364ee206@mail.kernel.org/T/ v2: - Replaced the approach of propagating errors from txLock() with proactive dmap validation. - Introduced dbValidateDmap() to check dmap page integrity (nblocks, nfree, start address, and tree structure). - Integrated dmap validation into dbFree(), dbUpdatePMap(), dbAlloc(), dbExtend(), dbAllocCtl(), dbAllocBottomUp(), and dbExtendFS(). - Reverted return type changes for functions in jfs_dtree.c and jfs_xtree.c from the previous version. https://lore.kernel.org/all/ff86d803-d687-48f6-9cc2-f3d35b27a666@mail.kernel.org/T/ v1: https://lore.kernel.org/all/9d2eba88-93bf-4f3c-a3b2-b554e1fffe80@mail.kernel.org/T/ --- diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c index a841cf21d..9bdbc55d8 100644 --- a/fs/jfs/jfs_dmap.c +++ b/fs/jfs/jfs_dmap.c @@ -98,6 +98,9 @@ static int blkstol2(s64 nb); static int cntlz(u32 value); static int cnttz(u32 word); +static bool db_validate_dmap(struct super_block *sb, const struct dmap *dp, + s64 expected_start); + static int dbAllocDmapBU(struct bmap * bmp, struct dmap * dp, s64 blkno, int nblocks); static int dbInitDmap(struct dmap * dp, s64 blkno, int nblocks); @@ -886,6 +889,12 @@ int dbAlloc(struct inode *ip, s64 hint, s64 nblocks, s64 * results) dp = (struct dmap *) mp->data; + if (!db_validate_dmap(ip->i_sb, dp, + blkno & ~(s64)(BPERDMAP - 1))) { + release_metapage(mp); + goto read_unlock; + } + /* first, try to satisfy the allocation request with the * blocks beginning at the hint. */ @@ -1902,7 +1911,9 @@ dbAllocCtl(struct bmap * bmp, s64 nblocks, int l2nb, s64 blkno, s64 * results) return -EIO; dp = (struct dmap *) mp->data; - if (dp->tree.budmin < 0) { + if (dp->tree.budmin < 0 || + !db_validate_dmap(bmp->db_ipbmap->i_sb, dp, + blkno & ~(s64)(BPERDMAP - 1))) { release_metapage(mp); return -EIO; } @@ -2134,6 +2145,18 @@ static int dbAllocDmap(struct bmap * bmp, struct dmap * dp, s64 blkno, return (rc); } +static bool db_validate_dmap(struct super_block *sb, const struct dmap *dp, + s64 expected_start) +{ + if (le64_to_cpu(dp->start) != expected_start) { + jfs_error(sb, "corrupt dmap page: start %lld expected %lld\n", + (long long)le64_to_cpu(dp->start), + (long long)expected_start); + return false; + } + + return true; +} /* * NAME: dbFreeDmap() base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482 -- This is an AI-generated patch subject to moderation. 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