tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
1
fork

Configure Feed

Select the types of activity you want to include in your feed.

hfs: validate record offset in hfsplus_bmap_alloc

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@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/67bcb4a6.050a0220.bbfd1.008f.GAE@google.com/
Signed-off-by: Yang Chenzhi <yang.chenzhi@vivo.com>
Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>
Link: https://lore.kernel.org/r/20250818141734.8559-2-yang.chenzhi@vivo.com
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>

authored by

Yang Chenzhi and committed by
Viacheslav Dubeyko 738d5a51 9282bc90

+48 -41
-41
fs/hfsplus/bnode.c
··· 18 18 #include "hfsplus_fs.h" 19 19 #include "hfsplus_raw.h" 20 20 21 - static inline 22 - bool is_bnode_offset_valid(struct hfs_bnode *node, int off) 23 - { 24 - bool is_valid = off < node->tree->node_size; 25 - 26 - if (!is_valid) { 27 - pr_err("requested invalid offset: " 28 - "NODE: id %u, type %#x, height %u, " 29 - "node_size %u, offset %d\n", 30 - node->this, node->type, node->height, 31 - node->tree->node_size, off); 32 - } 33 - 34 - return is_valid; 35 - } 36 - 37 - static inline 38 - int check_and_correct_requested_length(struct hfs_bnode *node, int off, int len) 39 - { 40 - unsigned int node_size; 41 - 42 - if (!is_bnode_offset_valid(node, off)) 43 - return 0; 44 - 45 - node_size = node->tree->node_size; 46 - 47 - if ((off + len) > node_size) { 48 - int new_len = (int)node_size - off; 49 - 50 - pr_err("requested length has been corrected: " 51 - "NODE: id %u, type %#x, height %u, " 52 - "node_size %u, offset %d, " 53 - "requested_len %d, corrected_len %d\n", 54 - node->this, node->type, node->height, 55 - node->tree->node_size, off, len, new_len); 56 - 57 - return new_len; 58 - } 59 - 60 - return len; 61 - } 62 21 63 22 /* Copy a specified range of bytes from the raw data of a node */ 64 23 void hfs_bnode_read(struct hfs_bnode *node, void *buf, int off, int len)
+6
fs/hfsplus/btree.c
··· 393 393 len = hfs_brec_lenoff(node, 2, &off16); 394 394 off = off16; 395 395 396 + if (!is_bnode_offset_valid(node, off)) { 397 + hfs_bnode_put(node); 398 + return ERR_PTR(-EIO); 399 + } 400 + len = check_and_correct_requested_length(node, off, len); 401 + 396 402 off += node->page_offset; 397 403 pagep = node->page + (off >> PAGE_SHIFT); 398 404 data = kmap_local_page(*pagep);
+42
fs/hfsplus/hfsplus_fs.h
··· 577 577 return class; 578 578 } 579 579 580 + static inline 581 + bool is_bnode_offset_valid(struct hfs_bnode *node, int off) 582 + { 583 + bool is_valid = off < node->tree->node_size; 584 + 585 + if (!is_valid) { 586 + pr_err("requested invalid offset: " 587 + "NODE: id %u, type %#x, height %u, " 588 + "node_size %u, offset %d\n", 589 + node->this, node->type, node->height, 590 + node->tree->node_size, off); 591 + } 592 + 593 + return is_valid; 594 + } 595 + 596 + static inline 597 + int check_and_correct_requested_length(struct hfs_bnode *node, int off, int len) 598 + { 599 + unsigned int node_size; 600 + 601 + if (!is_bnode_offset_valid(node, off)) 602 + return 0; 603 + 604 + node_size = node->tree->node_size; 605 + 606 + if ((off + len) > node_size) { 607 + int new_len = (int)node_size - off; 608 + 609 + pr_err("requested length has been corrected: " 610 + "NODE: id %u, type %#x, height %u, " 611 + "node_size %u, offset %d, " 612 + "requested_len %d, corrected_len %d\n", 613 + node->this, node->type, node->height, 614 + node->tree->node_size, off, len, new_len); 615 + 616 + return new_len; 617 + } 618 + 619 + return len; 620 + } 621 + 580 622 /* compatibility */ 581 623 #define hfsp_mt2ut(t) (struct timespec64){ .tv_sec = __hfsp_mt2ut(t) } 582 624 #define hfsp_ut2mt(t) __hfsp_ut2mt((t).tv_sec)