[syzbot] [trace?] KASAN: use-after-free Read in ring_buffer_map

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f932fb9b4074 Merge tag 'v6.13-rc2-ksmbd-server-fixes' of g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=109b2d44580000
kernel config: https://syzkaller.appspot.com/x/.config?x=99a5586995ec03b2
dashboard link: https://syzkaller.appspot.com/bug?extid=345e4443a21200874b18
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13ca24f8580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14514730580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f0d0c95f5364/disk-f932fb9b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/201cf3c7a7b5/vmlinux-f932fb9b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fcb972084579/bzImage-f932fb9b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+345e44...@syzkaller.appspotmail.com

==================================================================
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
RIP: 0033:0x7f3a0489e9f9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd1dfacbc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f3a0489e9f9
RDX: 0000000000000040 RSI: 0000000000000009 RDI: 0000000000000000
RBP: 00007f3a049115f0 R08: 0000000000000003 R09: 0000000000008000
R10: 0000000000000013 R11: 0000000000000246 R12: 0000000000000001
R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
</TASK>

Allocated by task 5836:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
kasan_kmalloc include/linux/kasan.h:260 [inline]
__do_kmalloc_node mm/slub.c:4283 [inline]
__kmalloc_noprof+0x21a/0x4f0 mm/slub.c:4295
kmalloc_noprof include/linux/slab.h:905 [inline]
kmalloc_array_noprof include/linux/slab.h:946 [inline]
ring_buffer_map+0x1e1/0x9b0 kernel/trace/ring_buffer.c:7120
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 buggy address belongs to the object at ffff8880767dd280
which belongs to the cache kmalloc-32 of size 32
The buggy address is located 32 bytes to the right of
allocated 24-byte region [ffff8880767dd280, ffff8880767dd298)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x767dd
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801ac41780 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080400040 00000001f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52800(GFP_NOWAIT|__GFP_NORETRY|__GFP_COMP), pid 5833, tgid 5833 (sshd), ts 84990303308, free_ts 79508073557
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x2d1/0x350 mm/page_alloc.c:1556
prep_new_page mm/page_alloc.c:1564 [inline]
get_page_from_freelist+0xfce/0x2f80 mm/page_alloc.c:3474
__alloc_pages_noprof+0x223/0x25b0 mm/page_alloc.c:4751
alloc_pages_mpol_noprof+0x2c9/0x610 mm/mempolicy.c:2269
alloc_slab_page mm/slub.c:2408 [inline]
allocate_slab mm/slub.c:2574 [inline]
new_slab+0x2c9/0x410 mm/slub.c:2627
___slab_alloc+0xce2/0x1650 mm/slub.c:3815
__slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3905
__slab_alloc_node mm/slub.c:3980 [inline]
slab_alloc_node mm/slub.c:4141 [inline]
__kmalloc_cache_noprof+0xf6/0x420 mm/slub.c:4309
kmalloc_noprof include/linux/slab.h:901 [inline]
slab_free_hook mm/slub.c:2290 [inline]
slab_free mm/slub.c:4598 [inline]
kmem_cache_free+0x2ef/0x4c0 mm/slub.c:4700
file_free fs/file_table.c:76 [inline]
fput+0x3ad/0x440 fs/file_table.c:505
path_openat+0xec1/0x2d60 fs/namei.c:3996
do_filp_open+0x20c/0x470 fs/namei.c:4014
do_sys_openat2+0x17a/0x1e0 fs/open.c:1402
do_sys_open fs/open.c:1417 [inline]
__do_sys_openat fs/open.c:1433 [inline]
__se_sys_openat fs/open.c:1428 [inline]
__x64_sys_openat+0x175/0x210 fs/open.c:1428
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
page last free pid 5832 tgid 5832 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1127 [inline]
free_unref_page+0x661/0x1080 mm/page_alloc.c:2657
__folio_put+0x32a/0x450 mm/swap.c:112
folio_put include/linux/mm.h:1488 [inline]
put_page+0x21e/0x280 include/linux/mm.h:1560
anon_pipe_buf_release+0x11a/0x240 fs/pipe.c:128
pipe_buf_release include/linux/pipe_fs_i.h:219 [inline]
pipe_update_tail fs/pipe.c:224 [inline]
pipe_read+0x641/0x13f0 fs/pipe.c:344
new_sync_read fs/read_write.c:484 [inline]
vfs_read+0xa4c/0xbe0 fs/read_write.c:565
ksys_read+0x207/0x250 fs/read_write.c:708
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

Memory state around the buggy address:
ffff8880767dd180: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
ffff8880767dd200: fa fb fb fb fc fc fc fc 00 00 00 fc fc fc fc fc
>ffff8880767dd280: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff8880767dd300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880767dd380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
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[Edward Adam Davis]

#syz test:https://github.com/ea1davis/linux.git kt/syz

[syzbot]

> #syz test:https://github.com/ea1davis/linux.git kt/syz

unknown command "test:https://github.com/ea1davis/linux.git"

>
>

[Edward Adam Davis]

#syz test: https://github.com/ea1davis/linux kt/syz

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+345e44...@syzkaller.appspotmail.com
Tested-by: syzbot+345e44...@syzkaller.appspotmail.com

Tested on:

commit: f5f643b6 ring-buffer: Fix oob in __rb_map_vma
git tree: https://github.com/ea1davis/linux kt/syz
console output: https://syzkaller.appspot.com/x/log.txt?x=147bfcdf980000
kernel config: https://syzkaller.appspot.com/x/.config?x=e8d97faf7b870c89

dashboard link: https://syzkaller.appspot.com/bug?extid=345e4443a21200874b18
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.

[Edward Adam Davis]

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]

Reported-by: syzbot+345e44...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=345e4443a21200874b18
Tested-by: syzbot+345e44...@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <ead...@qq.com>
---
kernel/trace/ring_buffer.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 7e257e855dd1..15c43d7415d5 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -7019,6 +7019,9 @@ 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 */
+ if (((nr_subbufs + 1) << subbuf_order) < pgoff)
+ return -EINVAL;
+
nr_pages = ((nr_subbufs + 1) << subbuf_order) - pgoff; /* + meta-page */

nr_vma_pages = vma_pages(vma);
--
2.47.0

[Steven Rostedt]

A proper fix is being discussed here:

https://lore.kernel.org/linux-trace-kernel/20241216164931.5...@gmail.com/

Thank you,

-- Steve

[Edward Adam Davis]

First, my fix is the first one.
Second, the root cause of the problem is an overflow when calculating nr_pages.

>
> https://lore.kernel.org/linux-trace-kernel/20241216164931.5...@gmail.com/
>
> Thank you,
>
> -- Steve
>

The calculation of nr_pages below overflows because the pgoff value is 8,
the nr_subbufs value is 3, and the subbuf_order value is 0.

> > nr_pages = ((nr_subbufs + 1) << subbuf_order) - pgoff; /* + meta-page */
> >
> > nr_vma_pages = vma_pages(vma);

BR,
Edward

[Steven Rostedt]

On Wed, 18 Dec 2024 07:43:46 +0800
Edward Adam Davis <ead...@qq.com> wrote:

> >
> > A proper fix is being discussed here:
> First, my fix is the first one.

Yes I saw that.

> Second, the root cause of the problem is an overflow when calculating nr_pages.
> >
> > https://lore.kernel.org/linux-trace-kernel/20241216164931.5...@gmail.com/
> >
> > Thank you,
> >
> > -- Steve
> >
> The calculation of nr_pages below overflows because the pgoff value is 8,
> the nr_subbufs value is 3, and the subbuf_order value is 0.

So basically you are saying that passing in the the mmap with the pgoff is
what's causing it.

> > > nr_pages = ((nr_subbufs + 1) << subbuf_order) - pgoff; /* + meta-page */
> > >
> > > nr_vma_pages = vma_pages(vma);

Thanks, I believe I now have a reproducer. And yes, I'll take your patch.
(If Vincent is OK with it).

Here's the reproducer:

------------------------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-------------------------

Thanks,


-- Steve

[Jeongjun Park]

> Steven Rostedt <ros...@goodmis.org> wrote:
>
> On Wed, 18 Dec 2024 07:43:46 +0800

> Edward Adam Davis <ead...@qq.com> wrote:
>
>>>
>>> A proper fix is being discussed here:
>> First, my fix is the first one.
>
> Yes I saw that.
>
>> Second, the root cause of the problem is an overflow when calculating nr_pages.
>>>
>>> https://lore.kernel.org/linux-trace-kernel/20241216164931.5...@gmail.com/
>>>
>>> Thank you,
>>>
>>> -- Steve
>>>

Oh, I did not propose a patch that fixes the root cause of this oob. My patch
is a separate patch that fixes the wrong order, such as reading the array
before checking the variable s with the WARN function in the loop. So I think
both of these patches should be applied.

Regards,

Jeongjun Park

[Steven Rostedt]

On Wed, 18 Dec 2024 09:13:43 +0000
Vincent Donnefort <vdonn...@google.com> wrote:

> And probably also
>
> Fixes: 117c39200d9d ("ring-buffer: Introducing ring-buffer mapping functions")

I don't require patch submitters to add Fixes tags. It's more the
responsibility of the maintainer to do that. I still have to validate it as
there's been several times someone adds a Fixes tag which wasn't the right
commit that it fixed.

-- Steve

[Steven Rostedt]

On Wed, 18 Dec 2024 14:31:31 +0000
Vincent Donnefort <vdonn...@google.com> wrote:

> Aside, there's a selftest to check for the overflow of subbufs with the
> mapping... but of course it didn't test with offset > nr_subbufs.
>
> Do you think it is worth to extend it to cover this case? I'm happy to do a
> quick patch.

Yes, it should check that case.

Thanks,

-- Steve

[Vincent Donnefort]

On Tue, Dec 17, 2024 at 07:40:15PM -0500, Steven Rostedt wrote:
> On Wed, 18 Dec 2024 07:43:46 +0800
> Edward Adam Davis <ead...@qq.com> wrote:
>
> > >
> > > A proper fix is being discussed here:
> > First, my fix is the first one.
>
> Yes I saw that.
>
> > Second, the root cause of the problem is an overflow when calculating nr_pages.
> > >
> > > https://lore.kernel.org/linux-trace-kernel/20241216164931.5...@gmail.com/
> > >
> > > Thank you,
> > >
> > > -- Steve
> > >
> > The calculation of nr_pages below overflows because the pgoff value is 8,
> > the nr_subbufs value is 3, and the subbuf_order value is 0.
>
> So basically you are saying that passing in the the mmap with the pgoff is
> what's causing it.
>
> > > > nr_pages = ((nr_subbufs + 1) << subbuf_order) - pgoff; /* + meta-page */
> > > >
> > > > nr_vma_pages = vma_pages(vma);
>
>
> Thanks, I believe I now have a reproducer. And yes, I'll take your patch.
> (If Vincent is OK with it).

I wanted to look at the reproducer sent by Jeongjung yesterday but got
preempted. My bad.

To avoid repeating the (nr_subbufs + 1) << subbuf_order How about?

- nr_pages = ((nr_subbufs + 1) << subbuf_order) - pgoff; /* + meta-page */
+ nr_pages = ((nr_subbufs + 1) << subbuf_order); /* + meta-page */
+
+ if (pgoff > nr_pages)
+ return -EINVAL;
+
+ nr_pages -= pgoff;

And probably also

Fixes: 117c39200d9d ("ring-buffer: Introducing ring-buffer mapping functions")

>

[Vincent Donnefort]

Ack.

Aside, there's a selftest to check for the overflow of subbufs with the
mapping... but of course it didn't test with offset > nr_subbufs.

Do you think it is worth to extend it to cover this case? I'm happy to do a
quick patch.

--
Vincent