CVE-2025-38226

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

media: vivid: Change the siize of the composing

syzkaller found a bug:

BUG: KASAN: vmalloc-out-of-bounds in tpg_fill_plane_pattern drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2608 [inline] BUG: KASAN: vmalloc-out-of-bounds in tpg_fill_plane_buffer+0x1a9c/0x5af0 drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2705 Write of size 1440 at addr ffffc9000d0ffda0 by task vivid-000-vid-c/5304

CPU: 0 UID: 0 PID: 5304 Comm: vivid-000-vid-c Not tainted 6.14.0-rc2-syzkaller-00039-g09fbf3d50205 #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014

Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0x169/0x550 mm/kasan/report.c:489 kasan_report+0x143/0x180 mm/kasan/report.c:602 kasan_check_range+0x282/0x290 mm/kasan/generic.c:189 __asan_memcpy+0x40/0x70 mm/kasan/shadow.c:106 tpg_fill_plane_pattern drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2608 [inline] tpg_fill_plane_buffer+0x1a9c/0x5af0 drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2705 vivid_fillbuff drivers/media/test-drivers/vivid/vivid-kthread-cap.c:470 [inline] vivid_thread_vid_cap_tick+0xf8e/0x60d0 drivers/media/test-drivers/vivid/vivid-kthread-cap.c:629 vivid_thread_vid_cap+0x8aa/0xf30 drivers/media/test-drivers/vivid/vivid-kthread-cap.c:767 kthread+0x7a9/0x920 kernel/kthread.c:464 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

The composition size cannot be larger than the size of fmt_cap_rect. So execute v4l2_rect_map_inside() even if has_compose_cap == 0.

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/00da1c767a6567e56f23dda586847586868ac064
• https://git.kernel.org/stable/c/57597d8db5bbda618ba2145b7e8a7e6f01b6a27e
• https://git.kernel.org/stable/c/5d89aa42534723400fefd46e26e053b9c382b4ee
• https://git.kernel.org/stable/c/635cea4f44c1ddae208666772c164eab5a6bce39
• https://git.kernel.org/stable/c/89b5ab822bf69867c3951dd0eb34b0314c38966b
• https://git.kernel.org/stable/c/c56398885716d97ee9bcadb2bc9663a8c1757a34
• https://git.kernel.org/stable/c/f6b1b0f8ba0b61d8b511df5649d57235f230c135
• https://git.kernel.org/stable/c/f83ac8d30c43fd902af7c84c480f216157b60ef0
• https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html
• https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html