From: Edward Adam Davis <eadavis@xxxxxx>
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-------------------------
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 117c39200d9d7 ("ring-buffer: Introducing ring-buffer mapping functions")
Link: https://lore.kernel.org/tencent_06924B6674ED771167C23CC336C097223609@xxxxxx
Reported-by: syzbot+345e4443a21200874b18@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=345e4443a21200874b18
Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
kernel/trace/ring_buffer.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 7e257e855dd1..60210fb5b211 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -7019,7 +7019,11 @@ static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer,
lockdep_assert_held(&cpu_buffer->mapping_lock);
nr_subbufs = cpu_buffer->nr_pages + 1; /* + reader-subbuf */
- nr_pages = ((nr_subbufs + 1) << subbuf_order) - pgoff; /* + meta-page */
+ nr_pages = ((nr_subbufs + 1) << subbuf_order); /* + meta-page */
+ if (nr_pages <= pgoff)
+ return -EINVAL;
+
+ nr_pages -= pgoff;
nr_vma_pages = vma_pages(vma);
if (!nr_vma_pages || nr_vma_pages > nr_pages)
--
2.45.2
