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Message-Id: <20250818141734.8559-2-yang.chenzhi@vivo.com>
Date: Mon, 18 Aug 2025 22:17:34 +0800
From: Chenzhi Yang <yang.chenzhi@...o.com>
To: slava@...eyko.com,
glaubitz@...sik.fu-berlin.de,
frank.li@...o.com
Cc: linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org,
Yang Chenzhi <yang.chenzhi@...o.com>,
syzbot+356aed408415a56543cd@...kaller.appspotmail.com
Subject: [PATCH 1/1] hfs: validate record offset in hfsplus_bmap_alloc
From: Yang Chenzhi <yang.chenzhi@...o.com>
hfsplus_bmap_alloc can trigger a crash if a
record offset or length is larger than node_size
[ 15.264282] BUG: KASAN: slab-out-of-bounds in hfsplus_bmap_alloc+0x887/0x8b0
[ 15.265192] Read of size 8 at addr ffff8881085ca188 by task test/183
[ 15.265949]
[ 15.266163] CPU: 0 UID: 0 PID: 183 Comm: test Not tainted 6.17.0-rc2-gc17b750b3ad9 #14 PREEMPT(voluntary)
[ 15.266165] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 15.266167] Call Trace:
[ 15.266168] <TASK>
[ 15.266169] dump_stack_lvl+0x53/0x70
[ 15.266173] print_report+0xd0/0x660
[ 15.266181] kasan_report+0xce/0x100
[ 15.266185] hfsplus_bmap_alloc+0x887/0x8b0
[ 15.266208] hfs_btree_inc_height.isra.0+0xd5/0x7c0
[ 15.266217] hfsplus_brec_insert+0x870/0xb00
[ 15.266222] __hfsplus_ext_write_extent+0x428/0x570
[ 15.266225] __hfsplus_ext_cache_extent+0x5e/0x910
[ 15.266227] hfsplus_ext_read_extent+0x1b2/0x200
[ 15.266233] hfsplus_file_extend+0x5a7/0x1000
[ 15.266237] hfsplus_get_block+0x12b/0x8c0
[ 15.266238] __block_write_begin_int+0x36b/0x12c0
[ 15.266251] block_write_begin+0x77/0x110
[ 15.266252] cont_write_begin+0x428/0x720
[ 15.266259] hfsplus_write_begin+0x51/0x100
[ 15.266262] cont_write_begin+0x272/0x720
[ 15.266270] hfsplus_write_begin+0x51/0x100
[ 15.266274] generic_perform_write+0x321/0x750
[ 15.266285] generic_file_write_iter+0xc3/0x310
[ 15.266289] __kernel_write_iter+0x2fd/0x800
[ 15.266296] dump_user_range+0x2ea/0x910
[ 15.266301] elf_core_dump+0x2a94/0x2ed0
[ 15.266320] vfs_coredump+0x1d85/0x45e0
[ 15.266349] get_signal+0x12e3/0x1990
[ 15.266357] arch_do_signal_or_restart+0x89/0x580
[ 15.266362] irqentry_exit_to_user_mode+0xab/0x110
[ 15.266364] asm_exc_page_fault+0x26/0x30
[ 15.266366] RIP: 0033:0x41bd35
[ 15.266367] Code: bc d1 f3 0f 7f 27 f3 0f 7f 6f 10 f3 0f 7f 77 20 f3 0f 7f 7f 30 49 83 c0 0f 49 29 d0 48 8d 7c 17 31 e9 9f 0b 00 00 66 0f ef c0 <f3> 0f 6f 0e f3 0f 6f 56 10 66 0f 74 c1 66 0f d7 d0 49 83 f8f
[ 15.266369] RSP: 002b:00007ffc9e62d078 EFLAGS: 00010283
[ 15.266371] RAX: 00007ffc9e62d100 RBX: 0000000000000000 RCX: 0000000000000000
[ 15.266372] RDX: 00000000000000e0 RSI: 0000000000000000 RDI: 00007ffc9e62d100
[ 15.266373] RBP: 0000400000000040 R08: 00000000000000e0 R09: 0000000000000000
[ 15.266374] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
[ 15.266375] R13: 0000000000000000 R14: 0000000000000000 R15: 0000400000000000
[ 15.266376] </TASK>
When calling hfsplus_bmap_alloc to allocate a free node, this function
first retrieves the bitmap from header node and map node using node->page
together with the offset and length from hfs_brec_lenoff
```
len = hfs_brec_lenoff(node, 2, &off16);
off = off16;
off += node->page_offset;
pagep = node->page + (off >> PAGE_SHIFT);
data = kmap_local_page(*pagep);
```
However, if the retrieved offset or length is invalid(i.e. exceeds
node_size), the code may end up accessing pages outside the allocated
range for this node.
This patch adds proper validation of both offset and length before use,
preventing out-of-bounds page access. Move is_bnode_offset_valid and
check_and_correct_requested_length to hfsplus_fs.h, as they may be
required by other functions.
Reported-by: syzbot+356aed408415a56543cd@...kaller.appspotmail.com
Closes: https://lore.kernel.org/all/67bcb4a6.050a0220.bbfd1.008f.GAE@google.com/
Signed-off-by: Yang Chenzhi <yang.chenzhi@...o.com>
---
fs/hfsplus/bnode.c | 41 ----------------------------------------
fs/hfsplus/btree.c | 6 ++++++
fs/hfsplus/hfsplus_fs.h | 42 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 48 insertions(+), 41 deletions(-)
diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c
index 14f4995588ff..407d5152eb41 100644
--- a/fs/hfsplus/bnode.c
+++ b/fs/hfsplus/bnode.c
@@ -18,47 +18,6 @@
#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)
diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
index 9e1732a2b92a..fe6a54c4083c 100644
--- a/fs/hfsplus/btree.c
+++ b/fs/hfsplus/btree.c
@@ -393,6 +393,12 @@ struct hfs_bnode *hfs_bmap_alloc(struct hfs_btree *tree)
len = hfs_brec_lenoff(node, 2, &off16);
off = off16;
+ if (!is_bnode_offset_valid(node, off)) {
+ hfs_bnode_put(node);
+ return ERR_PTR(-EIO);
+ }
+ len = check_and_correct_requested_length(node, off, len);
+
off += node->page_offset;
pagep = node->page + (off >> PAGE_SHIFT);
data = kmap_local_page(*pagep);
diff --git a/fs/hfsplus/hfsplus_fs.h b/fs/hfsplus/hfsplus_fs.h
index 96a5c24813dd..49965cd45261 100644
--- a/fs/hfsplus/hfsplus_fs.h
+++ b/fs/hfsplus/hfsplus_fs.h
@@ -577,6 +577,48 @@ hfsplus_btree_lock_class(struct hfs_btree *tree)
return class;
}
+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;
+}
+
/* compatibility */
#define hfsp_mt2ut(t) (struct timespec64){ .tv_sec = __hfsp_mt2ut(t) }
#define hfsp_ut2mt(t) __hfsp_ut2mt((t).tv_sec)
--
2.43.0
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