KASAN: slab-out-of-bounds Read in qrtr_endpoint_post

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 1590a2e1 Merge tag 'acpi-5.8-rc3' of git://git.kernel.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1142febb100000
kernel config: https://syzkaller.appspot.com/x/.config?x=bf3aec367b9ab569
dashboard link: https://syzkaller.appspot.com/bug?extid=b8fe393f999a291a9ea6
compiler: gcc (GCC) 10.1.0-syz 20200507

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+b8fe39...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in qrtr_endpoint_post+0xf9b/0x1010 net/qrtr/qrtr.c:447
Read of size 4 at addr ffff88809df0ce44 by task syz-executor.2/29604

CPU: 1 PID: 29604 Comm: syz-executor.2 Not tainted 5.8.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x18f/0x20d lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xae/0x436 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
qrtr_endpoint_post+0xf9b/0x1010 net/qrtr/qrtr.c:447
qrtr_tun_write_iter+0xf5/0x180 net/qrtr/tun.c:92
call_write_iter include/linux/fs.h:1907 [inline]
new_sync_write+0x422/0x650 fs/read_write.c:484
__vfs_write+0xc9/0x100 fs/read_write.c:497
vfs_write+0x268/0x5d0 fs/read_write.c:559
ksys_write+0x12d/0x250 fs/read_write.c:612
do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:359
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45cb19
Code: Bad RIP value.
RSP: 002b:00007ff63f2a7c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000050dd80 RCX: 000000000045cb19
RDX: 0000000000000004 RSI: 0000000020000140 RDI: 0000000000000005
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000d1e R14: 00000000004cf76d R15: 00007ff63f2a86d4

Allocated by task 29604:
save_stack+0x1b/0x40 mm/kasan/common.c:48
set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:494
__do_kmalloc mm/slab.c:3656 [inline]
__kmalloc+0x17a/0x340 mm/slab.c:3665
kmalloc include/linux/slab.h:560 [inline]
kzalloc include/linux/slab.h:669 [inline]
qrtr_tun_write_iter+0x8a/0x180 net/qrtr/tun.c:83
call_write_iter include/linux/fs.h:1907 [inline]
new_sync_write+0x422/0x650 fs/read_write.c:484
__vfs_write+0xc9/0x100 fs/read_write.c:497
vfs_write+0x268/0x5d0 fs/read_write.c:559
ksys_write+0x12d/0x250 fs/read_write.c:612
do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:359
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 24714:
save_stack+0x1b/0x40 mm/kasan/common.c:48
set_track mm/kasan/common.c:56 [inline]
kasan_set_free_info mm/kasan/common.c:316 [inline]
__kasan_slab_free+0xf5/0x140 mm/kasan/common.c:455
__cache_free mm/slab.c:3426 [inline]
kfree+0x103/0x2c0 mm/slab.c:3757
kvm_destroy_vm_debugfs arch/x86/kvm/../../../virt/kvm/kvm_main.c:628 [inline]
kvm_destroy_vm+0x158/0xbe0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:801
kvm_put_kvm arch/x86/kvm/../../../virt/kvm/kvm_main.c:843 [inline]
kvm_vcpu_release+0xc2/0x110 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2979
__fput+0x33c/0x880 fs/file_table.c:281
task_work_run+0xdd/0x190 kernel/task_work.c:123
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_usermode_loop arch/x86/entry/common.c:216 [inline]
__prepare_exit_to_usermode+0x1e9/0x1f0 arch/x86/entry/common.c:246
do_syscall_64+0x6c/0xe0 arch/x86/entry/common.c:368
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff88809df0ce40
which belongs to the cache kmalloc-32 of size 32
The buggy address is located 4 bytes inside of
32-byte region [ffff88809df0ce40, ffff88809df0ce60)
The buggy address belongs to the page:
page:ffffea000277c300 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88809df0cfc1
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00027c0a88 ffffea00027b7c08 ffff8880aa0001c0
raw: ffff88809df0cfc1 ffff88809df0c000 000000010000003f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88809df0cd00: 00 01 fc fc fc fc fc fc 00 01 fc fc fc fc fc fc
ffff88809df0cd80: 00 fc fc fc fc fc fc fc 06 fc fc fc fc fc fc fc
>ffff88809df0ce00: fb fb fb fb fc fc fc fc 04 fc fc fc fc fc fc fc
^
ffff88809df0ce80: 00 01 fc fc fc fc fc fc fb fb fb fb fc fc fc fc
ffff88809df0cf00: fb fb fb fb fc fc fc fc 00 00 00 fc fc fc fc fc
==================================================================


---
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[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: 1590a2e1 Merge tag 'acpi-5.8-rc3' of git://git.kernel.org/..
git tree: upstream

console output: https://syzkaller.appspot.com/x/log.txt?x=14b2b503100000

kernel config: https://syzkaller.appspot.com/x/.config?x=bf3aec367b9ab569
dashboard link: https://syzkaller.appspot.com/bug?extid=b8fe393f999a291a9ea6
compiler: gcc (GCC) 10.1.0-syz 20200507

userspace arch: i386
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=109e6b55100000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13671a3d100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+b8fe39...@syzkaller.appspotmail.com

==================================================================

BUG: KASAN: slab-out-of-bounds in qrtr_endpoint_post+0xeeb/0x1010 net/qrtr/qrtr.c:462
Read of size 2 at addr ffff88809de50c48 by task syz-executor531/6806

CPU: 0 PID: 6806 Comm: syz-executor531 Not tainted 5.8.0-rc2-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x18f/0x20d lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xae/0x436 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530

qrtr_endpoint_post+0xeeb/0x1010 net/qrtr/qrtr.c:462

qrtr_tun_write_iter+0xf5/0x180 net/qrtr/tun.c:92
call_write_iter include/linux/fs.h:1907 [inline]

do_iter_readv_writev+0x567/0x780 fs/read_write.c:694
do_iter_write+0x188/0x5f0 fs/read_write.c:999
compat_writev+0x1ea/0x390 fs/read_write.c:1352
do_compat_pwritev64+0x180/0x1b0 fs/read_write.c:1401
do_syscall_32_irqs_on+0x3f/0x60 arch/x86/entry/common.c:403
__do_fast_syscall_32 arch/x86/entry/common.c:448 [inline]
do_fast_syscall_32+0x7f/0x120 arch/x86/entry/common.c:474
entry_SYSENTER_compat+0x6d/0x7c arch/x86/entry/entry_64_compat.S:138
RIP: 0023:0xf7f8f569
Code: Bad RIP value.
RSP: 002b:00000000ffda5ffc EFLAGS: 00000292 ORIG_RAX: 000000000000014e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000020000440
RDX: 0000000000000001 RSI: 0000000000000000 RDI: 00000000080bb528
RBP: 0000000000000012 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 6806:

save_stack+0x1b/0x40 mm/kasan/common.c:48
set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:494
__do_kmalloc mm/slab.c:3656 [inline]
__kmalloc+0x17a/0x340 mm/slab.c:3665
kmalloc include/linux/slab.h:560 [inline]
kzalloc include/linux/slab.h:669 [inline]
qrtr_tun_write_iter+0x8a/0x180 net/qrtr/tun.c:83
call_write_iter include/linux/fs.h:1907 [inline]

do_iter_readv_writev+0x567/0x780 fs/read_write.c:694
do_iter_write+0x188/0x5f0 fs/read_write.c:999
compat_writev+0x1ea/0x390 fs/read_write.c:1352
do_compat_pwritev64+0x180/0x1b0 fs/read_write.c:1401
do_syscall_32_irqs_on+0x3f/0x60 arch/x86/entry/common.c:403
__do_fast_syscall_32 arch/x86/entry/common.c:448 [inline]
do_fast_syscall_32+0x7f/0x120 arch/x86/entry/common.c:474
entry_SYSENTER_compat+0x6d/0x7c arch/x86/entry/entry_64_compat.S:138

Freed by task 1:

save_stack+0x1b/0x40 mm/kasan/common.c:48
set_track mm/kasan/common.c:56 [inline]
kasan_set_free_info mm/kasan/common.c:316 [inline]
__kasan_slab_free+0xf5/0x140 mm/kasan/common.c:455
__cache_free mm/slab.c:3426 [inline]
kfree+0x103/0x2c0 mm/slab.c:3757

tomoyo_path_perm+0x234/0x3f0 security/tomoyo/file.c:842
security_inode_getattr+0xcf/0x140 security/security.c:1278
vfs_getattr fs/stat.c:121 [inline]
vfs_statx+0x170/0x390 fs/stat.c:206
vfs_lstat include/linux/fs.h:3301 [inline]
__do_sys_newlstat+0x91/0x110 fs/stat.c:374
do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:359
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff88809de50c40

which belongs to the cache kmalloc-32 of size 32

The buggy address is located 8 bytes inside of
32-byte region [ffff88809de50c40, ffff88809de50c60)

The buggy address belongs to the page:

page:ffffea0002779400 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88809de50fc1
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea000277e008 ffffea0002761c88 ffff8880aa0001c0
raw: ffff88809de50fc1 ffff88809de50000 000000010000003f 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff88809de50b00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
ffff88809de50b80: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
>ffff88809de50c00: fb fb fb fb fc fc fc fc 04 fc fc fc fc fc fc fc
^
ffff88809de50c80: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
ffff88809de50d00: fb fb fb fb fc fc fc fc 00 01 fc fc fc fc fc fc
==================================================================

[Manivannan Sadhasivam]

Hi Bjorn,

Hmm. Is this due to the fact that we are not checking the length of the
kbuf allocated in qrtr_tun_write_iter()? The length derived from
'iov_iter_count(from)' gets used directly and that might be causing the
out of bound access error here.

Thanks,
Mani

[Dan Carpenter]

This code assumes that the user passed in enough data for a
qrtr_hdr_v1 or qrtr_hdr_v2 struct, but it's not necessarily true. If
the buffer is too small then it will read beyond the end.

Reported-by: Manivannan Sadhasivam <manivannan...@linaro.org>
Reported-by: syzbot+b8fe39...@syzkaller.appspotmail.com
Fixes: 194ccc88297a ("net: qrtr: Support decoding incoming v2 packets")
Signed-off-by: Dan Carpenter <dan.ca...@oracle.com>
---
net/qrtr/qrtr.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c
index 2d8d6131bc5f..7eccbbf6f8ad 100644
--- a/net/qrtr/qrtr.c
+++ b/net/qrtr/qrtr.c
@@ -427,7 +427,7 @@ int qrtr_endpoint_post(struct qrtr_endpoint *ep, const void *data, size_t len)
unsigned int ver;
size_t hdrlen;

- if (len & 3)
+ if (len == 0 || len & 3)
return -EINVAL;

skb = netdev_alloc_skb(NULL, len);
@@ -441,6 +441,8 @@ int qrtr_endpoint_post(struct qrtr_endpoint *ep, const void *data, size_t len)

switch (ver) {
case QRTR_PROTO_VER_1:
+ if (len < sizeof(*v1))
+ goto err;
v1 = data;
hdrlen = sizeof(*v1);

@@ -454,6 +456,8 @@ int qrtr_endpoint_post(struct qrtr_endpoint *ep, const void *data, size_t len)
size = le32_to_cpu(v1->size);
break;
case QRTR_PROTO_VER_2:
+ if (len < sizeof(*v2))
+ goto err;
v2 = data;
hdrlen = sizeof(*v2) + v2->optlen;

--
2.27.0

[David Miller]

From: Dan Carpenter <dan.ca...@oracle.com>
Date: Tue, 30 Jun 2020 14:46:15 +0300

> This code assumes that the user passed in enough data for a
> qrtr_hdr_v1 or qrtr_hdr_v2 struct, but it's not necessarily true. If
> the buffer is too small then it will read beyond the end.
>
> Reported-by: Manivannan Sadhasivam <manivannan...@linaro.org>
> Reported-by: syzbot+b8fe39...@syzkaller.appspotmail.com
> Fixes: 194ccc88297a ("net: qrtr: Support decoding incoming v2 packets")
> Signed-off-by: Dan Carpenter <dan.ca...@oracle.com>

Applied and queued up for -stable, thanks Dan.