hfsplus: fix slab-out-of-bounds read in hfsplus_strcasecmp()

The hfsplus_strcasecmp() logic can trigger the issue:

[  117.317703][ T9855] ==================================================================
[  117.318353][ T9855] BUG: KASAN: slab-out-of-bounds in hfsplus_strcasecmp+0x1bc/0x490
[  117.318991][ T9855] Read of size 2 at addr ffff88802160f40c by task repro/9855
[  117.319577][ T9855]
[  117.319773][ T9855] CPU: 0 UID: 0 PID: 9855 Comm: repro Not tainted 6.17.0-rc6 #33 PREEMPT(full)
[  117.319780][ T9855] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[  117.319783][ T9855] Call Trace:
[  117.319785][ T9855]  <TASK>
[  117.319788][ T9855]  dump_stack_lvl+0x1c1/0x2a0
[  117.319795][ T9855]  ? __virt_addr_valid+0x1c8/0x5c0
[  117.319803][ T9855]  ? __pfx_dump_stack_lvl+0x10/0x10
[  117.319808][ T9855]  ? rcu_is_watching+0x15/0xb0
[  117.319816][ T9855]  ? lock_release+0x4b/0x3e0
[  117.319821][ T9855]  ? __kasan_check_byte+0x12/0x40
[  117.319828][ T9855]  ? __virt_addr_valid+0x1c8/0x5c0
[  117.319835][ T9855]  ? __virt_addr_valid+0x4a5/0x5c0
[  117.319842][ T9855]  print_report+0x17e/0x7e0
[  117.319848][ T9855]  ? __virt_addr_valid+0x1c8/0x5c0
[  117.319855][ T9855]  ? __virt_addr_valid+0x4a5/0x5c0
[  117.319862][ T9855]  ? __phys_addr+0xd3/0x180
[  117.319869][ T9855]  ? hfsplus_strcasecmp+0x1bc/0x490
[  117.319876][ T9855]  kasan_report+0x147/0x180
[  117.319882][ T9855]  ? hfsplus_strcasecmp+0x1bc/0x490
[  117.319891][ T9855]  hfsplus_strcasecmp+0x1bc/0x490
[  117.319900][ T9855]  ? __pfx_hfsplus_cat_case_cmp_key+0x10/0x10
[  117.319906][ T9855]  hfs_find_rec_by_key+0xa9/0x1e0
[  117.319913][ T9855]  __hfsplus_brec_find+0x18e/0x470
[  117.319920][ T9855]  ? __pfx_hfsplus_bnode_find+0x10/0x10
[  117.319926][ T9855]  ? __pfx_hfs_find_rec_by_key+0x10/0x10
[  117.319933][ T9855]  ? __pfx___hfsplus_brec_find+0x10/0x10
[  117.319942][ T9855]  hfsplus_brec_find+0x28f/0x510
[  117.319949][ T9855]  ? __pfx_hfs_find_rec_by_key+0x10/0x10
[  117.319956][ T9855]  ? __pfx_hfsplus_brec_find+0x10/0x10
[  117.319963][ T9855]  ? __kmalloc_noprof+0x2a9/0x510
[  117.319969][ T9855]  ? hfsplus_find_init+0x8c/0x1d0
[  117.319976][ T9855]  hfsplus_brec_read+0x2b/0x120
[  117.319983][ T9855]  hfsplus_lookup+0x2aa/0x890
[  117.319990][ T9855]  ? __pfx_hfsplus_lookup+0x10/0x10
[  117.320003][ T9855]  ? d_alloc_parallel+0x2f0/0x15e0
[  117.320008][ T9855]  ? __lock_acquire+0xaec/0xd80
[  117.320013][ T9855]  ? __pfx_d_alloc_parallel+0x10/0x10
[  117.320019][ T9855]  ? __raw_spin_lock_init+0x45/0x100
[  117.320026][ T9855]  ? __init_waitqueue_head+0xa9/0x150
[  117.320034][ T9855]  __lookup_slow+0x297/0x3d0
[  117.320039][ T9855]  ? __pfx___lookup_slow+0x10/0x10
[  117.320045][ T9855]  ? down_read+0x1ad/0x2e0
[  117.320055][ T9855]  lookup_slow+0x53/0x70
[  117.320065][ T9855]  walk_component+0x2f0/0x430
[  117.320073][ T9855]  path_lookupat+0x169/0x440
[  117.320081][ T9855]  filename_lookup+0x212/0x590
[  117.320089][ T9855]  ? __pfx_filename_lookup+0x10/0x10
[  117.320098][ T9855]  ? strncpy_from_user+0x150/0x290
[  117.320105][ T9855]  ? getname_flags+0x1e5/0x540
[  117.320112][ T9855]  user_path_at+0x3a/0x60
[  117.320117][ T9855]  __x64_sys_umount+0xee/0x160
[  117.320123][ T9855]  ? __pfx___x64_sys_umount+0x10/0x10
[  117.320129][ T9855]  ? do_syscall_64+0xb7/0x3a0
[  117.320135][ T9855]  ? entry_SYSCALL_64_after_hwframe+0x77/0x7f
[  117.320141][ T9855]  ? entry_SYSCALL_64_after_hwframe+0x77/0x7f
[  117.320145][ T9855]  do_syscall_64+0xf3/0x3a0
[  117.320150][ T9855]  ? exc_page_fault+0x9f/0xf0
[  117.320154][ T9855]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
[  117.320158][ T9855] RIP: 0033:0x7f7dd7908b07
[  117.320163][ T9855] Code: 23 0d 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 08
[  117.320167][ T9855] RSP: 002b:00007ffd5ebd9698 EFLAGS: 00000202 ORIG_RAX: 00000000000000a6
[  117.320172][ T9855] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f7dd7908b07
[  117.320176][ T9855] RDX: 0000000000000009 RSI: 0000000000000009 RDI: 00007ffd5ebd9740
[  117.320179][ T9855] RBP: 00007ffd5ebda780 R08: 0000000000000005 R09: 00007ffd5ebd9530
[  117.320181][ T9855] R10: 00007f7dd799bfc0 R11: 0000000000000202 R12: 000055e2008b32d0
[  117.320184][ T9855] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[  117.320189][ T9855]  </TASK>
[  117.320190][ T9855]
[  117.351311][ T9855] Allocated by task 9855:
[  117.351683][ T9855]  kasan_save_track+0x3e/0x80
[  117.352093][ T9855]  __kasan_kmalloc+0x8d/0xa0
[  117.352490][ T9855]  __kmalloc_noprof+0x288/0x510
[  117.352914][ T9855]  hfsplus_find_init+0x8c/0x1d0
[  117.353342][ T9855]  hfsplus_lookup+0x19c/0x890
[  117.353747][ T9855]  __lookup_slow+0x297/0x3d0
[  117.354148][ T9855]  lookup_slow+0x53/0x70
[  117.354514][ T9855]  walk_component+0x2f0/0x430
[  117.354921][ T9855]  path_lookupat+0x169/0x440
[  117.355325][ T9855]  filename_lookup+0x212/0x590
[  117.355740][ T9855]  user_path_at+0x3a/0x60
[  117.356115][ T9855]  __x64_sys_umount+0xee/0x160
[  117.356529][ T9855]  do_syscall_64+0xf3/0x3a0
[  117.356920][ T9855]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
[  117.357429][ T9855]
[  117.357636][ T9855] The buggy address belongs to the object at ffff88802160f000
[  117.357636][ T9855]  which belongs to the cache kmalloc-2k of size 2048
[  117.358827][ T9855] The buggy address is located 0 bytes to the right of
[  117.358827][ T9855]  allocated 1036-byte region [ffff88802160f000, ffff88802160f40c)
[  117.360061][ T9855]
[  117.360266][ T9855] The buggy address belongs to the physical page:
[  117.360813][ T9855] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x21608
[  117.361562][ T9855] head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
[  117.362285][ T9855] flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
[  117.362929][ T9855] page_type: f5(slab)
[  117.363282][ T9855] raw: 00fff00000000040 ffff88801a842f00 ffffea0000932000 dead000000000002
[  117.364015][ T9855] raw: 0000000000000000 0000000080080008 00000000f5000000 0000000000000000
[  117.364750][ T9855] head: 00fff00000000040 ffff88801a842f00 ffffea0000932000 dead000000000002
[  117.365491][ T9855] head: 0000000000000000 0000000080080008 00000000f5000000 0000000000000000
[  117.366232][ T9855] head: 00fff00000000003 ffffea0000858201 00000000ffffffff 00000000ffffffff
[  117.366968][ T9855] head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
[  117.367711][ T9855] page dumped because: kasan: bad access detected
[  117.368259][ T9855] page_owner tracks the page as allocated
[  117.368745][ T9855] page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN1
[  117.370541][ T9855]  post_alloc_hook+0x240/0x2a0
[  117.370954][ T9855]  get_page_from_freelist+0x2101/0x21e0
[  117.371435][ T9855]  __alloc_frozen_pages_noprof+0x274/0x380
[  117.371935][ T9855]  alloc_pages_mpol+0x241/0x4b0
[  117.372360][ T9855]  allocate_slab+0x8d/0x380
[  117.372752][ T9855]  ___slab_alloc+0xbe3/0x1400
[  117.373159][ T9855]  __kmalloc_cache_noprof+0x296/0x3d0
[  117.373621][ T9855]  nexthop_net_init+0x75/0x100
[  117.374038][ T9855]  ops_init+0x35c/0x5c0
[  117.374400][ T9855]  setup_net+0x10c/0x320
[  117.374768][ T9855]  copy_net_ns+0x31b/0x4d0
[  117.375156][ T9855]  create_new_namespaces+0x3f3/0x720
[  117.375613][ T9855]  unshare_nsproxy_namespaces+0x11c/0x170
[  117.376094][ T9855]  ksys_unshare+0x4ca/0x8d0
[  117.376477][ T9855]  __x64_sys_unshare+0x38/0x50
[  117.376879][ T9855]  do_syscall_64+0xf3/0x3a0
[  117.377265][ T9855] page last free pid 9110 tgid 9110 stack trace:
[  117.377795][ T9855]  __free_frozen_pages+0xbeb/0xd50
[  117.378229][ T9855]  __put_partials+0x152/0x1a0
[  117.378625][ T9855]  put_cpu_partial+0x17c/0x250
[  117.379026][ T9855]  __slab_free+0x2d4/0x3c0
[  117.379404][ T9855]  qlist_free_all+0x97/0x140
[  117.379790][ T9855]  kasan_quarantine_reduce+0x148/0x160
[  117.380250][ T9855]  __kasan_slab_alloc+0x22/0x80
[  117.380662][ T9855]  __kmalloc_noprof+0x232/0x510
[  117.381074][ T9855]  tomoyo_supervisor+0xc0a/0x1360
[  117.381498][ T9855]  tomoyo_env_perm+0x149/0x1e0
[  117.381903][ T9855]  tomoyo_find_next_domain+0x15ad/0x1b90
[  117.382378][ T9855]  tomoyo_bprm_check_security+0x11c/0x180
[  117.382859][ T9855]  security_bprm_check+0x89/0x280
[  117.383289][ T9855]  bprm_execve+0x8f1/0x14a0
[  117.383673][ T9855]  do_execveat_common+0x528/0x6b0
[  117.384103][ T9855]  __x64_sys_execve+0x94/0xb0
[  117.384500][ T9855]
[  117.384706][ T9855] Memory state around the buggy address:
[  117.385179][ T9855]  ffff88802160f300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[  117.385854][ T9855]  ffff88802160f380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[  117.386534][ T9855] >ffff88802160f400: 00 04 fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[  117.387204][ T9855]                       ^
[  117.387566][ T9855]  ffff88802160f480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[  117.388243][ T9855]  ffff88802160f500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[  117.388918][ T9855] ==================================================================

The issue takes place if the length field of struct hfsplus_unistr
is bigger than HFSPLUS_MAX_STRLEN. The patch simply checks
the length of comparing strings. And if the strings' length
is bigger than HFSPLUS_MAX_STRLEN, then it is corrected
to this value.

v2
The string length correction has been added for hfsplus_strcmp().

Reported-by: Jiaming Zhang <r772577952@gmail.com>
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>
cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
cc: Yangtao Li <frank.li@vivo.com>
cc: linux-fsdevel@vger.kernel.org
cc: syzkaller@googlegroups.com
Link: https://lore.kernel.org/r/20250919191243.1370388-1-slava@dubeyko.com
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>

diff --git a/fs/hfsplus/unicode.c b/fs/hfsplus/unicode.c
index 862ba27f1628a803c42e0af23df06cb7ce44dc1d..11e08a4a18b2957a53c25a29ecf78db5dbee6bac 100644 (file)
--- a/fs/hfsplus/unicode.c
+++ b/fs/hfsplus/unicode.c
@@ -40,6 +40,18 @@ int hfsplus_strcasecmp(const struct hfsplus_unistr *s1,
        p1 = s1->unicode;
        p2 = s2->unicode;
 
+       if (len1 > HFSPLUS_MAX_STRLEN) {
+               len1 = HFSPLUS_MAX_STRLEN;
+               pr_err("invalid length %u has been corrected to %d\n",
+                       be16_to_cpu(s1->length), len1);
+       }
+
+       if (len2 > HFSPLUS_MAX_STRLEN) {
+               len2 = HFSPLUS_MAX_STRLEN;
+               pr_err("invalid length %u has been corrected to %d\n",
+                       be16_to_cpu(s2->length), len2);
+       }
+
        while (1) {
                c1 = c2 = 0;
 
@@ -74,6 +86,18 @@ int hfsplus_strcmp(const struct hfsplus_unistr *s1,
        p1 = s1->unicode;
        p2 = s2->unicode;
 
+       if (len1 > HFSPLUS_MAX_STRLEN) {
+               len1 = HFSPLUS_MAX_STRLEN;
+               pr_err("invalid length %u has been corrected to %d\n",
+                       be16_to_cpu(s1->length), len1);
+       }
+
+       if (len2 > HFSPLUS_MAX_STRLEN) {
+               len2 = HFSPLUS_MAX_STRLEN;
+               pr_err("invalid length %u has been corrected to %d\n",
+                       be16_to_cpu(s2->length), len2);
+       }
+
        for (len = min(len1, len2); len > 0; len--) {
                c1 = be16_to_cpu(*p1);
                c2 = be16_to_cpu(*p2);