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smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=L7vHFGFu; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="L7vHFGFu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4224AC4CEF9; Thu, 2 Oct 2025 15:30:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1759419047; bh=NJ7XCA6Dc9p9hflmX4O8mtJD0I2QF3CtUt2w3mLYIlc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=L7vHFGFuP4SYufGlUOULRBthshPgx03Hm3fobeHxHY3Cm8+MPlCRYAxZZsPXGMjRG nWrJHsBLJjvDwM5z5fr9R+Son4ubSF8G7+5Vc3mnYVS/GTlM+c3UcBbBHMEcB0+H1g FSl1T5h9cW8ujBXx1GGANeIQXlMTiAdcWcS818X2QSnjQcSwrHEjlHRk+zw82M9ct8 J5dMhSYcROEa9vxmNwCGQWvbWy0MI5bvSNmilyi+GvOgdFy45bSuoSvPN5/aTommPP /xTOX3DQJ9Ov3W5REXy99RGG6wczGjH7HnTDukpTggw48nQRX1Y8yNm6To5I4wzYwK WxoTUxhQCuxmQ== From: Sasha Levin To: patches@lists.linux.dev, stable@vger.kernel.org Cc: Viacheslav Dubeyko , syzbot , John Paul Adrian Glaubitz , Yangtao Li , linux-fsdevel@vger.kernel.org, Sasha Levin Subject: [PATCH AUTOSEL 6.17-5.4] hfsplus: fix KMSAN uninit-value issue in hfsplus_delete_cat() Date: Thu, 2 Oct 2025 11:30:03 -0400 Message-ID: <20251002153025.2209281-16-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251002153025.2209281-1-sashal@kernel.org> References: <20251002153025.2209281-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.17 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Viacheslav Dubeyko [ Upstream commit 9b3d15a758910bb98ba8feb4109d99cc67450ee4 ] The syzbot reported issue in hfsplus_delete_cat(): [ 70.682285][ T9333] ===================================================== [ 70.682943][ T9333] BUG: KMSAN: uninit-value in hfsplus_subfolders_dec+0x1d7/0x220 [ 70.683640][ T9333] hfsplus_subfolders_dec+0x1d7/0x220 [ 70.684141][ T9333] hfsplus_delete_cat+0x105d/0x12b0 [ 70.684621][ T9333] hfsplus_rmdir+0x13d/0x310 [ 70.685048][ T9333] vfs_rmdir+0x5ba/0x810 [ 70.685447][ T9333] do_rmdir+0x964/0xea0 [ 70.685833][ T9333] __x64_sys_rmdir+0x71/0xb0 [ 70.686260][ T9333] x64_sys_call+0xcd8/0x3cf0 [ 70.686695][ T9333] do_syscall_64+0xd9/0x1d0 [ 70.687119][ T9333] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 70.687646][ T9333] [ 70.687856][ T9333] Uninit was stored to memory at: [ 70.688311][ T9333] hfsplus_subfolders_inc+0x1c2/0x1d0 [ 70.688779][ T9333] hfsplus_create_cat+0x148e/0x1800 [ 70.689231][ T9333] hfsplus_mknod+0x27f/0x600 [ 70.689730][ T9333] hfsplus_mkdir+0x5a/0x70 [ 70.690146][ T9333] vfs_mkdir+0x483/0x7a0 [ 70.690545][ T9333] do_mkdirat+0x3f2/0xd30 [ 70.690944][ T9333] __x64_sys_mkdir+0x9a/0xf0 [ 70.691380][ T9333] x64_sys_call+0x2f89/0x3cf0 [ 70.691816][ T9333] do_syscall_64+0xd9/0x1d0 [ 70.692229][ T9333] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 70.692773][ T9333] [ 70.692990][ T9333] Uninit was stored to memory at: [ 70.693469][ T9333] hfsplus_subfolders_inc+0x1c2/0x1d0 [ 70.693960][ T9333] hfsplus_create_cat+0x148e/0x1800 [ 70.694438][ T9333] hfsplus_fill_super+0x21c1/0x2700 [ 70.694911][ T9333] mount_bdev+0x37b/0x530 [ 70.695320][ T9333] hfsplus_mount+0x4d/0x60 [ 70.695729][ T9333] legacy_get_tree+0x113/0x2c0 [ 70.696167][ T9333] vfs_get_tree+0xb3/0x5c0 [ 70.696588][ T9333] do_new_mount+0x73e/0x1630 [ 70.697013][ T9333] path_mount+0x6e3/0x1eb0 [ 70.697425][ T9333] __se_sys_mount+0x733/0x830 [ 70.697857][ T9333] __x64_sys_mount+0xe4/0x150 [ 70.698269][ T9333] x64_sys_call+0x2691/0x3cf0 [ 70.698704][ T9333] do_syscall_64+0xd9/0x1d0 [ 70.699117][ T9333] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 70.699730][ T9333] [ 70.699946][ T9333] Uninit was created at: [ 70.700378][ T9333] __alloc_pages_noprof+0x714/0xe60 [ 70.700843][ T9333] alloc_pages_mpol_noprof+0x2a2/0x9b0 [ 70.701331][ T9333] alloc_pages_noprof+0xf8/0x1f0 [ 70.701774][ T9333] allocate_slab+0x30e/0x1390 [ 70.702194][ T9333] ___slab_alloc+0x1049/0x33a0 [ 70.702635][ T9333] kmem_cache_alloc_lru_noprof+0x5ce/0xb20 [ 70.703153][ T9333] hfsplus_alloc_inode+0x5a/0xd0 [ 70.703598][ T9333] alloc_inode+0x82/0x490 [ 70.703984][ T9333] iget_locked+0x22e/0x1320 [ 70.704428][ T9333] hfsplus_iget+0x5c/0xba0 [ 70.704827][ T9333] hfsplus_btree_open+0x135/0x1dd0 [ 70.705291][ T9333] hfsplus_fill_super+0x1132/0x2700 [ 70.705776][ T9333] mount_bdev+0x37b/0x530 [ 70.706171][ T9333] hfsplus_mount+0x4d/0x60 [ 70.706579][ T9333] legacy_get_tree+0x113/0x2c0 [ 70.707019][ T9333] vfs_get_tree+0xb3/0x5c0 [ 70.707444][ T9333] do_new_mount+0x73e/0x1630 [ 70.707865][ T9333] path_mount+0x6e3/0x1eb0 [ 70.708270][ T9333] __se_sys_mount+0x733/0x830 [ 70.708711][ T9333] __x64_sys_mount+0xe4/0x150 [ 70.709158][ T9333] x64_sys_call+0x2691/0x3cf0 [ 70.709630][ T9333] do_syscall_64+0xd9/0x1d0 [ 70.710053][ T9333] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 70.710611][ T9333] [ 70.710842][ T9333] CPU: 3 UID: 0 PID: 9333 Comm: repro Not tainted 6.12.0-rc6-dirty #17 [ 70.711568][ T9333] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 70.712490][ T9333] ===================================================== [ 70.713085][ T9333] Disabling lock debugging due to kernel taint [ 70.713618][ T9333] Kernel panic - not syncing: kmsan.panic set ... [ 70.714159][ T9333] CPU: 3 UID: 0 PID: 9333 Comm: repro Tainted: G B 6.12.0-rc6-dirty #17 [ 70.715007][ T9333] Tainted: [B]=BAD_PAGE [ 70.715365][ T9333] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 70.716311][ T9333] Call Trace: [ 70.716621][ T9333] [ 70.716899][ T9333] dump_stack_lvl+0x1fd/0x2b0 [ 70.717350][ T9333] dump_stack+0x1e/0x30 [ 70.717743][ T9333] panic+0x502/0xca0 [ 70.718116][ T9333] ? kmsan_get_metadata+0x13e/0x1c0 [ 70.718611][ T9333] kmsan_report+0x296/0x2a0 [ 70.719038][ T9333] ? __msan_metadata_ptr_for_load_4+0x24/0x40 [ 70.719859][ T9333] ? __msan_warning+0x96/0x120 [ 70.720345][ T9333] ? hfsplus_subfolders_dec+0x1d7/0x220 [ 70.720881][ T9333] ? hfsplus_delete_cat+0x105d/0x12b0 [ 70.721412][ T9333] ? hfsplus_rmdir+0x13d/0x310 [ 70.721880][ T9333] ? vfs_rmdir+0x5ba/0x810 [ 70.722458][ T9333] ? do_rmdir+0x964/0xea0 [ 70.722883][ T9333] ? __x64_sys_rmdir+0x71/0xb0 [ 70.723397][ T9333] ? x64_sys_call+0xcd8/0x3cf0 [ 70.723915][ T9333] ? do_syscall_64+0xd9/0x1d0 [ 70.724454][ T9333] ? entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 70.725110][ T9333] ? vprintk_emit+0xd1f/0xe60 [ 70.725616][ T9333] ? vprintk_default+0x3f/0x50 [ 70.726175][ T9333] ? vprintk+0xce/0xd0 [ 70.726628][ T9333] ? _printk+0x17e/0x1b0 [ 70.727129][ T9333] ? __msan_metadata_ptr_for_load_4+0x24/0x40 [ 70.727739][ T9333] ? kmsan_get_metadata+0x13e/0x1c0 [ 70.728324][ T9333] __msan_warning+0x96/0x120 [ 70.728854][ T9333] hfsplus_subfolders_dec+0x1d7/0x220 [ 70.729479][ T9333] hfsplus_delete_cat+0x105d/0x12b0 [ 70.729984][ T9333] ? kmsan_get_shadow_origin_ptr+0x4a/0xb0 [ 70.730646][ T9333] ? __msan_metadata_ptr_for_load_4+0x24/0x40 [ 70.731296][ T9333] ? kmsan_get_metadata+0x13e/0x1c0 [ 70.731863][ T9333] hfsplus_rmdir+0x13d/0x310 [ 70.732390][ T9333] ? __pfx_hfsplus_rmdir+0x10/0x10 [ 70.732919][ T9333] vfs_rmdir+0x5ba/0x810 [ 70.733416][ T9333] ? kmsan_get_shadow_origin_ptr+0x4a/0xb0 [ 70.734044][ T9333] do_rmdir+0x964/0xea0 [ 70.734537][ T9333] __x64_sys_rmdir+0x71/0xb0 [ 70.735032][ T9333] x64_sys_call+0xcd8/0x3cf0 [ 70.735579][ T9333] do_syscall_64+0xd9/0x1d0 [ 70.736092][ T9333] ? irqentry_exit+0x16/0x60 [ 70.736637][ T9333] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 70.737269][ T9333] RIP: 0033:0x7fa9424eafc9 [ 70.737775][ T9333] Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 48 [ 70.739844][ T9333] RSP: 002b:00007fff099cd8d8 EFLAGS: 00000202 ORIG_RAX: 0000000000000054 [ 70.740760][ T9333] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fa9424eafc9 [ 70.741642][ T9333] RDX: 006c6f72746e6f63 RSI: 000000000000000a RDI: 0000000020000100 [ 70.742543][ T9333] RBP: 00007fff099cd8e0 R08: 00007fff099cd910 R09: 00007fff099cd910 [ 70.743376][ T9333] R10: 0000000000000000 R11: 0000000000000202 R12: 0000565430642260 [ 70.744247][ T9333] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 70.745082][ T9333] The main reason of the issue that struct hfsplus_inode_info has not been properly initialized for the case of root folder. In the case of root folder, hfsplus_fill_super() calls the hfsplus_iget() that implements only partial initialization of struct hfsplus_inode_info and subfolders field is not initialized by hfsplus_iget() logic. This patch implements complete initialization of struct hfsplus_inode_info in the hfsplus_iget() logic with the goal to prevent likewise issues for the case of root folder. Reported-by: syzbot Closes: https://syzkaller.appspot.com/bug?extid=fdedff847a0e5e84c39f Signed-off-by: Viacheslav Dubeyko cc: John Paul Adrian Glaubitz cc: Yangtao Li cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20250825225103.326401-1-slava@dubeyko.com Signed-off-by: Viacheslav Dubeyko Signed-off-by: Sasha Levin --- LLM Generated explanations, may be completely bogus: Based on my comprehensive analysis of this commit, I can now provide my recommendation. **YES** ## Detailed Analysis ### Bug Description and Impact This commit fixes a **KMSAN (Kernel Memory Sanitizer) uninitialized value bug** in the hfsplus filesystem that has existed since **2014** (11 years). The issue occurs when: 1. **Root Cause**: The `hfsplus_iget()` function in fs/hfsplus/super.c:59 only partially initialized `struct hfsplus_inode_info`, leaving several fields (notably `subfolders`) uninitialized with random memory contents from the slab allocator 2. **Trigger**: When operations like `rmdir` are performed on HFSX filesystems, `hfsplus_subfolders_dec()` at fs/hfsplus/catalog.c:236 reads the uninitialized `subfolders` field 3. **Consequence**: Undefined behavior, KMSAN warnings, potential kernel panic (when kmsan.panic is set), and potential security implications from using uninitialized kernel memory The syzbot report (https://syzkaller.appspot.com/bug?extid=fdedff847a0e5e84c39f) shows this bug has been **reported since 2022 with multiple recurrences through 2025**, affecting kernel version 6.12.0-rc6 and likely all versions since 3.14. ### Code Changes Analysis **Before the fix** (fs/hfsplus/super.c:71-77), only 7 fields were initialized: - `open_dir_list`, `open_dir_lock`, `extents_lock`, `flags`, `extent_state`, `rsrc_inode`, `opencnt` **After the fix** (fs/hfsplus/super.c:71-92), **ALL 19 fields** are now initialized: - Added initialization for: `first_blocks`, `clump_blocks`, `alloc_blocks`, `cached_start`, `cached_blocks`, `first_extents`, `cached_extents`, `create_date`, `linkid`, `fs_blocks`, `userflags`, **`subfolders`** (the key fix), and `phys_size` The fix is **defensive** - it ensures complete initialization rather than just fixing the immediate `subfolders` issue, preventing similar bugs in the future. ### Backport Suitability Assessment **✓ Fixes a real bug**: Yes - syzbot reports since 2022, reproducible issue **✓ Affects users**: Yes - anyone mounting HFSX filesystems (HFS+ variant used by macOS) **✓ Small and contained**: Yes - 23 lines changed in one function in one file **✓ No architectural changes**: Correct - only adds field initialization **✓ Low regression risk**: Very low - adds initialization that should have been there from the start; no behavior changes, only ensures defined values instead of random memory **✓ No dependencies**: Standalone fix with no dependencies on other commits **✓ Self-contained**: Changes confined to `hfsplus_iget()` function **✓ Follows stable rules**: - Obviously correct (just initialization) - Fixes real bug (KMSAN reports, undefined behavior) - Less than 100 lines - Important bugfix with minimal risk ### Security and Stability Implications 1. **Memory safety**: Uninitialized memory can contain sensitive data from previous allocations 2. **Filesystem integrity**: The `subfolders` counter being uninitialized can lead to incorrect filesystem state 3. **System stability**: Can cause kernel panic when memory sanitizers are enabled 4. **Data correctness**: Undefined behavior in filesystem code is particularly dangerous ### Historical Context The `subfolders` field was added in **commit d7d673a591701f (2014-03-10)** to support HFSX subfolder counting, but `hfsplus_iget()` was never updated to initialize it. This bug has affected **all kernel versions from 3.14 onwards** (approximately 11 years). ### Recommendation This commit is an **excellent candidate for backporting** to all stable kernel trees from v3.14 onwards. It fixes a long-standing memory initialization bug with minimal risk and clear benefit for filesystem stability and security. fs/hfsplus/super.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/fs/hfsplus/super.c b/fs/hfsplus/super.c index 86351bdc89859..2f215d1daf6d9 100644 --- a/fs/hfsplus/super.c +++ b/fs/hfsplus/super.c @@ -68,13 +68,26 @@ struct inode *hfsplus_iget(struct super_block *sb, unsigned long ino) if (!(inode->i_state & I_NEW)) return inode; - INIT_LIST_HEAD(&HFSPLUS_I(inode)->open_dir_list); - spin_lock_init(&HFSPLUS_I(inode)->open_dir_lock); - mutex_init(&HFSPLUS_I(inode)->extents_lock); - HFSPLUS_I(inode)->flags = 0; + atomic_set(&HFSPLUS_I(inode)->opencnt, 0); + HFSPLUS_I(inode)->first_blocks = 0; + HFSPLUS_I(inode)->clump_blocks = 0; + HFSPLUS_I(inode)->alloc_blocks = 0; + HFSPLUS_I(inode)->cached_start = U32_MAX; + HFSPLUS_I(inode)->cached_blocks = 0; + memset(HFSPLUS_I(inode)->first_extents, 0, sizeof(hfsplus_extent_rec)); + memset(HFSPLUS_I(inode)->cached_extents, 0, sizeof(hfsplus_extent_rec)); HFSPLUS_I(inode)->extent_state = 0; + mutex_init(&HFSPLUS_I(inode)->extents_lock); HFSPLUS_I(inode)->rsrc_inode = NULL; - atomic_set(&HFSPLUS_I(inode)->opencnt, 0); + HFSPLUS_I(inode)->create_date = 0; + HFSPLUS_I(inode)->linkid = 0; + HFSPLUS_I(inode)->flags = 0; + HFSPLUS_I(inode)->fs_blocks = 0; + HFSPLUS_I(inode)->userflags = 0; + HFSPLUS_I(inode)->subfolders = 0; + INIT_LIST_HEAD(&HFSPLUS_I(inode)->open_dir_list); + spin_lock_init(&HFSPLUS_I(inode)->open_dir_lock); + HFSPLUS_I(inode)->phys_size = 0; if (inode->i_ino >= HFSPLUS_FIRSTUSER_CNID || inode->i_ino == HFSPLUS_ROOT_CNID) { -- 2.51.0