From: Viacheslav Dubeyko slava@dubeyko.com
[ Upstream commit c80aa2aaaa5e69d5219c6af8ef7e754114bd08d2 ]
The hfsplus_bnode_read() method can trigger the issue:
[ 174.852007][ T9784] ================================================================== [ 174.852709][ T9784] BUG: KASAN: slab-out-of-bounds in hfsplus_bnode_read+0x2f4/0x360 [ 174.853412][ T9784] Read of size 8 at addr ffff88810b5fc6c0 by task repro/9784 [ 174.854059][ T9784] [ 174.854272][ T9784] CPU: 1 UID: 0 PID: 9784 Comm: repro Not tainted 6.16.0-rc3 #7 PREEMPT(full) [ 174.854281][ T9784] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 174.854286][ T9784] Call Trace: [ 174.854289][ T9784] <TASK> [ 174.854292][ T9784] dump_stack_lvl+0x10e/0x1f0 [ 174.854305][ T9784] print_report+0xd0/0x660 [ 174.854315][ T9784] ? __virt_addr_valid+0x81/0x610 [ 174.854323][ T9784] ? __phys_addr+0xe8/0x180 [ 174.854330][ T9784] ? hfsplus_bnode_read+0x2f4/0x360 [ 174.854337][ T9784] kasan_report+0xc6/0x100 [ 174.854346][ T9784] ? hfsplus_bnode_read+0x2f4/0x360 [ 174.854354][ T9784] hfsplus_bnode_read+0x2f4/0x360 [ 174.854362][ T9784] hfsplus_bnode_dump+0x2ec/0x380 [ 174.854370][ T9784] ? __pfx_hfsplus_bnode_dump+0x10/0x10 [ 174.854377][ T9784] ? hfsplus_bnode_write_u16+0x83/0xb0 [ 174.854385][ T9784] ? srcu_gp_start+0xd0/0x310 [ 174.854393][ T9784] ? __mark_inode_dirty+0x29e/0xe40 [ 174.854402][ T9784] hfsplus_brec_remove+0x3d2/0x4e0 [ 174.854411][ T9784] __hfsplus_delete_attr+0x290/0x3a0 [ 174.854419][ T9784] ? __pfx_hfs_find_1st_rec_by_cnid+0x10/0x10 [ 174.854427][ T9784] ? __pfx___hfsplus_delete_attr+0x10/0x10 [ 174.854436][ T9784] ? __asan_memset+0x23/0x50 [ 174.854450][ T9784] hfsplus_delete_all_attrs+0x262/0x320 [ 174.854459][ T9784] ? __pfx_hfsplus_delete_all_attrs+0x10/0x10 [ 174.854469][ T9784] ? rcu_is_watching+0x12/0xc0 [ 174.854476][ T9784] ? __mark_inode_dirty+0x29e/0xe40 [ 174.854483][ T9784] hfsplus_delete_cat+0x845/0xde0 [ 174.854493][ T9784] ? __pfx_hfsplus_delete_cat+0x10/0x10 [ 174.854507][ T9784] hfsplus_unlink+0x1ca/0x7c0 [ 174.854516][ T9784] ? __pfx_hfsplus_unlink+0x10/0x10 [ 174.854525][ T9784] ? down_write+0x148/0x200 [ 174.854532][ T9784] ? __pfx_down_write+0x10/0x10 [ 174.854540][ T9784] vfs_unlink+0x2fe/0x9b0 [ 174.854549][ T9784] do_unlinkat+0x490/0x670 [ 174.854557][ T9784] ? __pfx_do_unlinkat+0x10/0x10 [ 174.854565][ T9784] ? __might_fault+0xbc/0x130 [ 174.854576][ T9784] ? getname_flags.part.0+0x1c5/0x550 [ 174.854584][ T9784] __x64_sys_unlink+0xc5/0x110 [ 174.854592][ T9784] do_syscall_64+0xc9/0x480 [ 174.854600][ T9784] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 174.854608][ T9784] RIP: 0033:0x7f6fdf4c3167 [ 174.854614][ T9784] Code: f0 ff ff 73 01 c3 48 8b 0d 26 0d 0e 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 08 [ 174.854622][ T9784] RSP: 002b:00007ffcb948bca8 EFLAGS: 00000206 ORIG_RAX: 0000000000000057 [ 174.854630][ T9784] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f6fdf4c3167 [ 174.854636][ T9784] RDX: 00007ffcb948bcc0 RSI: 00007ffcb948bcc0 RDI: 00007ffcb948bd50 [ 174.854641][ T9784] RBP: 00007ffcb948cd90 R08: 0000000000000001 R09: 00007ffcb948bb40 [ 174.854645][ T9784] R10: 00007f6fdf564fc0 R11: 0000000000000206 R12: 0000561e1bc9c2d0 [ 174.854650][ T9784] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 174.854658][ T9784] </TASK> [ 174.854661][ T9784] [ 174.879281][ T9784] Allocated by task 9784: [ 174.879664][ T9784] kasan_save_stack+0x20/0x40 [ 174.880082][ T9784] kasan_save_track+0x14/0x30 [ 174.880500][ T9784] __kasan_kmalloc+0xaa/0xb0 [ 174.880908][ T9784] __kmalloc_noprof+0x205/0x550 [ 174.881337][ T9784] __hfs_bnode_create+0x107/0x890 [ 174.881779][ T9784] hfsplus_bnode_find+0x2d0/0xd10 [ 174.882222][ T9784] hfsplus_brec_find+0x2b0/0x520 [ 174.882659][ T9784] hfsplus_delete_all_attrs+0x23b/0x320 [ 174.883144][ T9784] hfsplus_delete_cat+0x845/0xde0 [ 174.883595][ T9784] hfsplus_rmdir+0x106/0x1b0 [ 174.884004][ T9784] vfs_rmdir+0x206/0x690 [ 174.884379][ T9784] do_rmdir+0x2b7/0x390 [ 174.884751][ T9784] __x64_sys_rmdir+0xc5/0x110 [ 174.885167][ T9784] do_syscall_64+0xc9/0x480 [ 174.885568][ T9784] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 174.886083][ T9784] [ 174.886293][ T9784] The buggy address belongs to the object at ffff88810b5fc600 [ 174.886293][ T9784] which belongs to the cache kmalloc-192 of size 192 [ 174.887507][ T9784] The buggy address is located 40 bytes to the right of [ 174.887507][ T9784] allocated 152-byte region [ffff88810b5fc600, ffff88810b5fc698) [ 174.888766][ T9784] [ 174.888976][ T9784] The buggy address belongs to the physical page: [ 174.889533][ T9784] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10b5fc [ 174.890295][ T9784] flags: 0x57ff00000000000(node=1|zone=2|lastcpupid=0x7ff) [ 174.890927][ T9784] page_type: f5(slab) [ 174.891284][ T9784] raw: 057ff00000000000 ffff88801b4423c0 ffffea000426dc80 dead000000000002 [ 174.892032][ T9784] raw: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000 [ 174.892774][ T9784] page dumped because: kasan: bad access detected [ 174.893327][ T9784] page_owner tracks the page as allocated [ 174.893825][ T9784] page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52c00(GFP_NOIO|__GFP_NOWARN|__GFP_NO1 [ 174.895373][ T9784] post_alloc_hook+0x1c0/0x230 [ 174.895801][ T9784] get_page_from_freelist+0xdeb/0x3b30 [ 174.896284][ T9784] __alloc_frozen_pages_noprof+0x25c/0x2460 [ 174.896810][ T9784] alloc_pages_mpol+0x1fb/0x550 [ 174.897242][ T9784] new_slab+0x23b/0x340 [ 174.897614][ T9784] ___slab_alloc+0xd81/0x1960 [ 174.898028][ T9784] __slab_alloc.isra.0+0x56/0xb0 [ 174.898468][ T9784] __kmalloc_noprof+0x2b0/0x550 [ 174.898896][ T9784] usb_alloc_urb+0x73/0xa0 [ 174.899289][ T9784] usb_control_msg+0x1cb/0x4a0 [ 174.899718][ T9784] usb_get_string+0xab/0x1a0 [ 174.900133][ T9784] usb_string_sub+0x107/0x3c0 [ 174.900549][ T9784] usb_string+0x307/0x670 [ 174.900933][ T9784] usb_cache_string+0x80/0x150 [ 174.901355][ T9784] usb_new_device+0x1d0/0x19d0 [ 174.901786][ T9784] register_root_hub+0x299/0x730 [ 174.902231][ T9784] page last free pid 10 tgid 10 stack trace: [ 174.902757][ T9784] __free_frozen_pages+0x80c/0x1250 [ 174.903217][ T9784] vfree.part.0+0x12b/0xab0 [ 174.903645][ T9784] delayed_vfree_work+0x93/0xd0 [ 174.904073][ T9784] process_one_work+0x9b5/0x1b80 [ 174.904519][ T9784] worker_thread+0x630/0xe60 [ 174.904927][ T9784] kthread+0x3a8/0x770 [ 174.905291][ T9784] ret_from_fork+0x517/0x6e0 [ 174.905709][ T9784] ret_from_fork_asm+0x1a/0x30 [ 174.906128][ T9784] [ 174.906338][ T9784] Memory state around the buggy address: [ 174.906828][ T9784] ffff88810b5fc580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc [ 174.907528][ T9784] ffff88810b5fc600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 174.908222][ T9784] >ffff88810b5fc680: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc [ 174.908917][ T9784] ^ [ 174.909481][ T9784] ffff88810b5fc700: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 174.910432][ T9784] ffff88810b5fc780: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc [ 174.911401][ T9784] ==================================================================
The reason of the issue that code doesn't check the correctness of the requested offset and length. As a result, incorrect value of offset or/and length could result in access out of allocated memory.
This patch introduces is_bnode_offset_valid() method that checks the requested offset value. Also, it introduces check_and_correct_requested_length() method that checks and correct the requested length (if it is necessary). These methods are used in hfsplus_bnode_read(), hfsplus_bnode_write(), hfsplus_bnode_clear(), hfsplus_bnode_copy(), and hfsplus_bnode_move() with the goal to prevent the access out of allocated memory and triggering the crash.
Reported-by: Kun Hu huk23@m.fudan.edu.cn Reported-by: Jiaji Qin jjtan24@m.fudan.edu.cn Reported-by: Shuoran Bai baishuoran@hrbeu.edu.cn Signed-off-by: Viacheslav Dubeyko slava@dubeyko.com Link: https://lore.kernel.org/r/20250703214804.244077-1-slava@dubeyko.com Signed-off-by: Viacheslav Dubeyko slava@dubeyko.com Signed-off-by: Sasha Levin sashal@kernel.org ---
LLM Generated explanations, may be completely bogus:
I notice I was analyzing the wrong commit. Let me analyze the actual commit about hfsplus that was provided.
**YES** - This commit should be backported to stable kernel trees.
## Extensive Explanation:
### 1. **Critical Security Bug Fix** This commit fixes a serious **slab-out-of-bounds** vulnerability in the HFS+ filesystem driver. The KASAN report shows: ``` BUG: KASAN: slab-out-of-bounds in hfsplus_bnode_read+0x2f4/0x360 Read of size 8 at addr ffff88810b5fc6c0 by task repro/9784 ``` This is a memory safety bug that can lead to kernel crashes and potentially security exploits.
### 2. **Root Cause Analysis** The commit message clearly identifies the root cause:
"The reason of the issue that code doesn't check the correctness of
the requested offset and length. As a result, incorrect value of offset or/and length could result in access out of allocated memory."
The code changes confirm this by adding two new validation functions: - `is_bnode_offset_valid()` - validates that offsets don't exceed node boundaries - `check_and_correct_requested_length()` - ensures length doesn't cause reads beyond allocated memory
### 3. **Widespread Impact** The fix is applied to multiple critical HFS+ bnode operations: - `hfs_bnode_read()` - `hfs_bnode_write()` - `hfs_bnode_clear()` - `hfs_bnode_copy()` - `hfs_bnode_move()`
This indicates the vulnerability affects core filesystem operations that are commonly used.
### 4. **Meets Stable Criteria** According to stable kernel rules, this commit qualifies because: - **Fixes a real bug**: Out-of-bounds memory access that crashes the kernel - **Small and contained**: The fix adds simple bounds checking (~150 lines) - **Already in mainline**: Has been accepted into Linus's tree - **No new features**: Only adds safety checks, no functionality changes - **Security implications**: Memory corruption bugs are security- relevant
### 5. **Minimal Risk of Regression** The fix is conservative: - Only adds validation checks before existing operations - Logs errors when invalid parameters are detected - Attempts to correct lengths rather than failing operations - Doesn't change the fundamental behavior of working code
### 6. **Clear Reproducer** The commit includes a detailed KASAN trace from a reproducer, showing: - The exact call path through HFS+ deletion operations - Memory allocation details - The specific out-of-bounds access location
This indicates the bug is reproducible and the fix can be verified.
### 7. **Defensive Programming** The added checks follow good defensive programming practices: ```c if (!is_bnode_offset_valid(node, off)) return;
len = check_and_correct_requested_length(node, off, len); ``` These prevent crashes while maintaining compatibility.
### 8. **Critical Subsystem** Filesystem drivers are critical kernel components. Bugs in filesystem code can: - Lead to data corruption - Cause system crashes - Be exploited for privilege escalation - Affect any user mounting HFS+ filesystems
### Conclusion This commit fixes a serious memory safety vulnerability in the HFS+ filesystem driver that can cause kernel crashes and has potential security implications. The fix is well-contained, adds only necessary validation checks, and meets all criteria for stable kernel backporting. It should be backported to all stable kernels that include the HFS+ driver to protect users from this vulnerability.
fs/hfsplus/bnode.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 92 insertions(+)
diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c index 079ea80534f7..14f4995588ff 100644 --- a/fs/hfsplus/bnode.c +++ b/fs/hfsplus/bnode.c @@ -18,12 +18,68 @@ #include "hfsplus_fs.h" #include "hfsplus_raw.h"
+static inline +bool is_bnode_offset_valid(struct hfs_bnode *node, int off) +{ + bool is_valid = off < node->tree->node_size; + + if (!is_valid) { + pr_err("requested invalid offset: " + "NODE: id %u, type %#x, height %u, " + "node_size %u, offset %d\n", + node->this, node->type, node->height, + node->tree->node_size, off); + } + + return is_valid; +} + +static inline +int check_and_correct_requested_length(struct hfs_bnode *node, int off, int len) +{ + unsigned int node_size; + + if (!is_bnode_offset_valid(node, off)) + return 0; + + node_size = node->tree->node_size; + + if ((off + len) > node_size) { + int new_len = (int)node_size - off; + + pr_err("requested length has been corrected: " + "NODE: id %u, type %#x, height %u, " + "node_size %u, offset %d, " + "requested_len %d, corrected_len %d\n", + node->this, node->type, node->height, + node->tree->node_size, off, len, new_len); + + return new_len; + } + + return len; +} + /* Copy a specified range of bytes from the raw data of a node */ void hfs_bnode_read(struct hfs_bnode *node, void *buf, int off, int len) { struct page **pagep; int l;
+ if (!is_bnode_offset_valid(node, off)) + return; + + if (len == 0) { + pr_err("requested zero length: " + "NODE: id %u, type %#x, height %u, " + "node_size %u, offset %d, len %d\n", + node->this, node->type, node->height, + node->tree->node_size, off, len); + return; + } + + len = check_and_correct_requested_length(node, off, len); + off += node->page_offset; pagep = node->page + (off >> PAGE_SHIFT); off &= ~PAGE_MASK; @@ -81,6 +137,20 @@ void hfs_bnode_write(struct hfs_bnode *node, void *buf, int off, int len) struct page **pagep; int l;
+ if (!is_bnode_offset_valid(node, off)) + return; + + if (len == 0) { + pr_err("requested zero length: " + "NODE: id %u, type %#x, height %u, " + "node_size %u, offset %d, len %d\n", + node->this, node->type, node->height, + node->tree->node_size, off, len); + return; + } + + len = check_and_correct_requested_length(node, off, len); + off += node->page_offset; pagep = node->page + (off >> PAGE_SHIFT); off &= ~PAGE_MASK; @@ -109,6 +179,20 @@ void hfs_bnode_clear(struct hfs_bnode *node, int off, int len) struct page **pagep; int l;
+ if (!is_bnode_offset_valid(node, off)) + return; + + if (len == 0) { + pr_err("requested zero length: " + "NODE: id %u, type %#x, height %u, " + "node_size %u, offset %d, len %d\n", + node->this, node->type, node->height, + node->tree->node_size, off, len); + return; + } + + len = check_and_correct_requested_length(node, off, len); + off += node->page_offset; pagep = node->page + (off >> PAGE_SHIFT); off &= ~PAGE_MASK; @@ -133,6 +217,10 @@ void hfs_bnode_copy(struct hfs_bnode *dst_node, int dst, hfs_dbg(BNODE_MOD, "copybytes: %u,%u,%u\n", dst, src, len); if (!len) return; + + len = check_and_correct_requested_length(src_node, src, len); + len = check_and_correct_requested_length(dst_node, dst, len); + src += src_node->page_offset; dst += dst_node->page_offset; src_page = src_node->page + (src >> PAGE_SHIFT); @@ -187,6 +275,10 @@ void hfs_bnode_move(struct hfs_bnode *node, int dst, int src, int len) hfs_dbg(BNODE_MOD, "movebytes: %u,%u,%u\n", dst, src, len); if (!len) return; + + len = check_and_correct_requested_length(node, src, len); + len = check_and_correct_requested_length(node, dst, len); + src += node->page_offset; dst += node->page_offset; if (dst > src) {