linux-kernel - [PATCH V3] ring-buffer: fix overflow in __rb_map

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Message-ID: <tencent_06924B6674ED771167C23CC336C097223609@qq.com>
Date: Wed, 18 Dec 2024 21:36:55 +0800
From: Edward Adam Davis <eadavis@...com>
To: rostedt@...dmis.org
Cc: aha310510@...il.com,
	david@...hat.com,
	eadavis@...com,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	mathieu.desnoyers@...icios.com,
	mhiramat@...nel.org,
	syzbot+345e4443a21200874b18@...kaller.appspotmail.com,
	syzkaller-bugs@...glegroups.com,
	vdonnefort@...gle.com
Subject: [PATCH V3] ring-buffer: fix overflow in __rb_map_vma

syzbot report a slab-out-of-bounds in __rb_map_vma. [1]

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.

[1]
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

Reported-by: syzbot+345e4443a21200874b18@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=345e4443a21200874b18
Signed-off-by: Edward Adam Davis <eadavis@...com>
---
V1 -> V2: updated according to Vincent Donnefort's suggestion, to avoid repeating the (nr_subbufs + 1) << subbuf_order
V2 -> V3: Add equal condition judgment

 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..20f0e01b7a50 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)
-- 
2.47.0