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

tracing: Fix oob write in trace_seq_to_buffer()

syzbot reported this bug:

BUG: KASAN: slab-out-of-bounds in trace_seq_to_buffer kernel/trace/trace.c:1830 [inline] BUG: KASAN: slab-out-of-bounds in tracing_splice_read_pipe+0x6be/0xdd0 kernel/trace/trace.c:6822 Write of size 4507 at addr ffff888032b6b000 by task syz.2.320/7260

CPU: 1 UID: 0 PID: 7260 Comm: syz.2.320 Not tainted 6.15.0-rc1-syzkaller-00301-g3bde70a2c827 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:408 [inline] print_report+0xc3/0x670 mm/kasan/report.c:521 kasan_report+0xe0/0x110 mm/kasan/report.c:634 check_region_inline mm/kasan/generic.c:183 [inline] kasan_check_range+0xef/0x1a0 mm/kasan/generic.c:189 __asan_memcpy+0x3c/0x60 mm/kasan/shadow.c:106 trace_seq_to_buffer kernel/trace/trace.c:1830 [inline] tracing_splice_read_pipe+0x6be/0xdd0 kernel/trace/trace.c:6822 ….

It has been reported that trace_seq_to_buffer() tries to copy more data than PAGE_SIZE to buf. Therefore, to prevent this, we should use the smaller of trace_seq_used(&iter->seq) and PAGE_SIZE as an argument.

Affected Software

References

• https://git.kernel.org/stable/c/056ebbddb8faf4ddf83d005454dd78fc25c2d897
• https://git.kernel.org/stable/c/1a3f9482b50b74fa9421bff8ceecfefd0dc06f8f
• https://git.kernel.org/stable/c/1f27a3e93b8d674b24b27fcdbc6f72743cd96c0d
• https://git.kernel.org/stable/c/441021e5b3c7d9bd1b963590652c415929f3b157
• https://git.kernel.org/stable/c/c5d2b66c5ef5037b4b4360e5447605ff00ba1bd4
• https://git.kernel.org/stable/c/f5178c41bb43444a6008150fe6094497135d07cb