In the Linux kernel, the following vulnerability has been resolved:

udf: Fix a slab-out-of-bounds write bug in udf_find_entry()

Syzbot reported a slab-out-of-bounds Write bug:

loop0: detected capacity change from 0 to 2048

BUG: KASAN: slab-out-of-bounds in udf_find_entry+0x8a5/0x14f0 fs/udf/namei.c:253 Write of size 105 at addr ffff8880123ff896 by task syz-executor323/3610

CPU: 0 PID: 3610 Comm: syz-executor323 Not tainted 6.1.0-rc2-syzkaller-00105-gb229b6ca5abb #0 Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106 print_address_description+0x74/0x340 mm/kasan/report.c:284 print_report+0x107/0x1f0 mm/kasan/report.c:395 kasan_report+0xcd/0x100 mm/kasan/report.c:495 kasan_check_range+0x2a7/0x2e0 mm/kasan/generic.c:189 memcpy+0x3c/0x60 mm/kasan/shadow.c:66 udf_find_entry+0x8a5/0x14f0 fs/udf/namei.c:253 udf_lookup+0xef/0x340 fs/udf/namei.c:309 lookup_open fs/namei.c:3391 [inline] open_last_lookups fs/namei.c:3481 [inline] path_openat+0x10e6/0x2df0 fs/namei.c:3710 do_filp_open+0x264/0x4f0 fs/namei.c:3740 do_sys_openat2+0x124/0x4e0 fs/open.c:1310 do_sys_open fs/open.c:1326 [inline] __do_sys_creat fs/open.c:1402 [inline] __se_sys_creat fs/open.c:1396 [inline] __x64_sys_creat+0x11f/0x160 fs/open.c:1396 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7ffab0d164d9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffe1a7e6bb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000055 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007ffab0d164d9 RDX: 00007ffab0d164d9 RSI: 0000000000000000 RDI: 0000000020000180 RBP: 00007ffab0cd5a10 R08: 0000000000000000 R09: 0000000000000000 R10: 00005555573552c0 R11: 0000000000000246 R12: 00007ffab0cd5aa0 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 3610: kasan_save_stack mm/kasan/common.c:45 [inline] kasan_set_track+0x3d/0x60 mm/kasan/common.c:52 ____kasan_kmalloc mm/kasan/common.c:371 [inline] __kasan_kmalloc+0x97/0xb0 mm/kasan/common.c:380 kmalloc include/linux/slab.h:576 [inline] udf_find_entry+0x7b6/0x14f0 fs/udf/namei.c:243 udf_lookup+0xef/0x340 fs/udf/namei.c:309 lookup_open fs/namei.c:3391 [inline] open_last_lookups fs/namei.c:3481 [inline] path_openat+0x10e6/0x2df0 fs/namei.c:3710 do_filp_open+0x264/0x4f0 fs/namei.c:3740 do_sys_openat2+0x124/0x4e0 fs/open.c:1310 do_sys_open fs/open.c:1326 [inline] __do_sys_creat fs/open.c:1402 [inline] __se_sys_creat fs/open.c:1396 [inline] __x64_sys_creat+0x11f/0x160 fs/open.c:1396 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff8880123ff800 which belongs to the cache kmalloc-256 of size 256 The buggy address is located 150 bytes inside of 256-byte region [ffff8880123ff800, ffff8880123ff900)

The buggy address belongs to the physical page: page:ffffea000048ff80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x123fe head:ffffea000048ff80 order:1 compound_mapcount:0 compound_pincount:0 flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000010200 ffffea00004b8500 dead000000000003 ffff888012041b40 raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 0, migratetype Unmovable, gfp_mask 0x0(), pid 1, tgid 1 (swapper/0), ts 1841222404, free_ts 0 create_dummy_stack mm/page_owner.c: —truncated—

Weakness

The product writes data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer.

• Be wary that a language’s interface to native code may still be subject to overflows, even if the language itself is theoretically safe.

• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• Examples include the Safe C String Library (SafeStr) by Messier and Viega [REF-57], and the Strsafe.h library from Microsoft [REF-56]. These libraries provide safer versions of overflow-prone string-handling functions.

• Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.

• D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.

• Consider adhering to the following rules when allocating and managing an application’s memory:

• Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.

• Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.

• For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].

• Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment.

• For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].

References

• https://git.kernel.org/stable/c/03f9582a6a2ebd25a440896475c968428c4b63e7
• https://git.kernel.org/stable/c/583fdd98d94acba1e7225e5cc29063aef0741030
• https://git.kernel.org/stable/c/7a6051d734f1ed0031e2216f9a538621235c11a4
• https://git.kernel.org/stable/c/ac79001b8e603226fab17240a79cb9ef679d3cd9
• https://git.kernel.org/stable/c/c736ed8541605e3a25075bb1cbf8f38cb3083238
• https://git.kernel.org/stable/c/c8af247de385ce49afabc3bf1cf4fd455c94bfe8
• https://git.kernel.org/stable/c/d8971f410739a864c537e0ac29344a7b6c450232
• https://git.kernel.org/stable/c/f1517721c408631f09d54c743aa70cb07fd3eebd