CVE-2024-56368

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

ring-buffer: Fix overflow in __rb_map_vma

An overflow occurred when performing the following calculation:

nr_pages = ((nr_subbufs + 1) << subbuf_order) - pgoff;

Add a check before the calculation to avoid this problem.

syzbot reported this as a slab-out-of-bounds in __rb_map_vma:

BUG: KASAN: slab-out-of-bounds in __rb_map_vma+0x9ab/0xae0 kernel/trace/ring_buffer.c:7058 Read of size 8 at addr ffff8880767dd2b8 by task syz-executor187/5836

CPU: 0 UID: 0 PID: 5836 Comm: syz-executor187 Not tainted 6.13.0-rc2-syzkaller-00159-gf932fb9b4074 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024 Call Trace: <TASK> __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:378 [inline] print_report+0xc3/0x620 mm/kasan/report.c:489 kasan_report+0xd9/0x110 mm/kasan/report.c:602 __rb_map_vma+0x9ab/0xae0 kernel/trace/ring_buffer.c:7058 ring_buffer_map+0x56e/0x9b0 kernel/trace/ring_buffer.c:7138 tracing_buffers_mmap+0xa6/0x120 kernel/trace/trace.c:8482 call_mmap include/linux/fs.h:2183 [inline] mmap_file mm/internal.h:124 [inline] __mmap_new_file_vma mm/vma.c:2291 [inline] __mmap_new_vma mm/vma.c:2355 [inline] __mmap_region+0x1786/0x2670 mm/vma.c:2456 mmap_region+0x127/0x320 mm/mmap.c:1348 do_mmap+0xc00/0xfc0 mm/mmap.c:496 vm_mmap_pgoff+0x1ba/0x360 mm/util.c:580 ksys_mmap_pgoff+0x32c/0x5c0 mm/mmap.c:542 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:89 [inline] __se_sys_mmap arch/x86/kernel/sys_x86_64.c:82 [inline] __x64_sys_mmap+0x125/0x190 arch/x86/kernel/sys_x86_64.c:82 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The reproducer for this bug is:

------------------------8<------------------------- #include <fcntl.h> #include <stdlib.h> #include <unistd.h> #include <asm/types.h> #include <sys/mman.h>

int main(int argc, char **argv) { int page_size = getpagesize(); int fd; void *meta;

system("echo 1 > /sys/kernel/tracing/buffer_size_kb");
fd = open("/sys/kernel/tracing/per_cpu/cpu0/trace_pipe_raw", O_RDONLY);

meta = mmap(NULL, page_size, PROT_READ, MAP_SHARED, fd, page_size * 5);

} ------------------------>8-------------------------

This vulnerability is evaluated as a Moderate impact because exploitation requires local access with elevated privileges, such as CAP_SYS_ADMIN, to open and map the kernel tracing buffer. On Red Hat Enterprise Linux systems, access to the tracefs interface is restricted to root and privileged administrators by default. Although triggering the flaw can cause an out-of-bounds read resulting in a system crash or potential memory leak, the prerequisite of high administrative privileges significantly limits the risk exposure.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.