Re: [Linux-kernel-mentees] [PATCH net] Bluetooth: Fix NULL pointer dereference in amp_read_loc_assoc_final_data()
On Wed, Mar 3, 2021 at 11:11 AM Gopal Tiwari wrote: > > Hi, > > I tried to search the patch for one of the bugzilla reported (Internal) > https://bugzilla.redhat.com/show_bug.cgi?id=1916057 with the traces > > [ 405.938525] Workqueue: hci0 hci_rx_work [bluetooth] > [ 405.941360] RIP: 0010:amp_read_loc_assoc_final_data+0xfc/0x1c0 [bluetooth] > [ 405.944740] Code: 89 44 24 29 48 b8 00 00 00 00 00 fc ff df 0f b6 04 02 84 > c0 74 08 3c 01 0f 8e 9d 00 00 00 0f b7 85 c0 03 00 00 66 89 44 24 2b 41 > 80 4c 24 30 04 4c 8d 64 24 68 48 89 ee 4c 89 e7 e8 3d 48 fe > [ 405.952396] RSP: 0018:88802ea0f838 EFLAGS: 00010246 > [ 405.955368] RAX: RBX: 111005d41f08 RCX: > dc00 > [ 405.958669] RDX: 1110254cc878 RSI: 88802000 RDI: > 88812a6643c0 > [ 405.961980] RBP: 88812a664000 R08: R09: > > [ 405.965319] R10: 88802ea0fd00 R11: R12: > > [ 405.968624] R13: 0041 R14: 88802b836800 R15: > 8881250570c0 > [ 405.971989] FS: () GS:888055a0() > knlGS: > [ 405.975645] CS: 0010 DS: ES: CR0: 80050033 > [ 405.978755] CR2: 0030 CR3: 2d20 CR4: > 00340ee0 > [ 405.982150] Call Trace: > [ 405.984768] ? amp_read_loc_assoc+0x170/0x170 [bluetooth] > [ 405.987875] ? rcu_read_unlock+0x50/0x50 > [ 405.990663] ? deref_stack_reg+0xf0/0xf0 > [ 405.993403] ? __module_address+0x3f/0x370 > [ 405.996184] ? hci_cmd_work+0x180/0x330 [bluetooth] > [ 405.999170] ? hci_conn_hash_lookup_handle+0x1a1/0x270 [bluetooth] > [ 406.002354] hci_event_packet+0x1476/0x7e00 [bluetooth] > [ 406.005407] ? arch_stack_walk+0x8f/0xf0 > [ 406.008206] ? ret_from_fork+0x27/0x50 > [ 406.010887] ? hci_cmd_complete_evt+0xbf70/0xbf70 [bluetooth] > [ 406.013933] ? stack_trace_save+0x8a/0xb0 > [ 406.016618] ? do_profile_hits.isra.4.cold.9+0x2d/0x2d > [ 406.019483] ? lock_acquire+0x1a3/0x970 > [ 406.022092] ? __wake_up_common_lock+0xaf/0x130 > > > I didn't found any solution upstream. After the vmcore analysis I found what > is wrong. And took reference from the following patch, which seems to be on > the similar line > > commit 6dfccd13db2ff2b709ef60a50163925d477549aa > Author: Anmol Karn > Date: Wed Sep 30 19:48:13 2020 +0530 > > Bluetooth: Fix null pointer dereference in hci_event_packet() > > AMP_MGR is getting derefernced in hci_phy_link_complete_evt(), when > called > from hci_event_packet() and there is a possibility, that > hcon->amp_mgr may > not be found when accessing after initialization of hcon. > > - net/bluetooth/hci_event.c:4945 > > How we can avoid this scenario. So I made the chages and tested. It worked or > avoided the kernel panic. But I really don't know that some one has already > posted the patch. I would have love to backport the patch, I was more of > looking for the fix. That's where I didn't applied the reported-by tag as I > thought it reported internal only. Hi Gopal, I think it's somewhat inherent to the current kernel unstructured processes with bugs being reported on mailing lists, bugzilla, distro-specific trackers. One useful thing, though, is searching Lore, e.g. searching for just the crashing function: https://lore.kernel.org/lkml/?q=amp_read_loc_assoc_final_data gives the report and the patch (if we filter out all entries produced by your patch, which obviously wasn't yet there before you wrote it :)): 12. [Linux-kernel-mentees] [PATCH net] Bluetooth: Fix NULL pointer dereference in amp_read_loc_assoc_final_data() - by Peilin Ye @ 2020-08-08 4:04 UTC [21%] 13. KASAN: null-ptr-deref Write in amp_read_loc_assoc_final_data - by syzbot @ 2020-07-31 17:04 UTC [13%] > Thanks & regards, > Gopal Tiwari > > > > - Original Message - > From: "Dmitry Vyukov" > To: "Peilin Ye" > Cc: "Marcel Holtmann" , "Johan Hedberg" > , "Andrei Emeltchenko" > , "Greg Kroah-Hartman" > , "David S. Miller" , "Jakub > Kicinski" , linux-kernel-ment...@lists.linuxfoundation.org, > "syzkaller-bugs" , "linux-bluetooth" > , "netdev" , "LKML" > , gtiw...@redhat.com, > syzbot+f4fb0eaafdb51c32a...@syzkaller.appspotmail.com > Sent: Wednesday, March 3, 2021 1:51:41 PM > Subject: Re: [Linux-kernel-mentees] [PATCH net] Bluetooth: Fix NULL pointer > dereference in amp_read_loc_assoc_final_data() > > On Sat, Aug 8, 2020 at 6:06 AM Peilin Ye wrote: > > > > Prevent amp_rea
Re: [Linux-kernel-mentees] [PATCH net] Bluetooth: Fix NULL pointer dereference in amp_read_loc_assoc_final_data()
Hi,
I tried to search the patch for one of the bugzilla reported (Internal)
https://bugzilla.redhat.com/show_bug.cgi?id=1916057 with the traces
[ 405.938525] Workqueue: hci0 hci_rx_work [bluetooth]
[ 405.941360] RIP: 0010:amp_read_loc_assoc_final_data+0xfc/0x1c0 [bluetooth]
[ 405.944740] Code: 89 44 24 29 48 b8 00 00 00 00 00 fc ff df 0f b6 04 02 84
c0 74 08 3c 01 0f 8e 9d 00 00 00 0f b7 85 c0 03 00 00 66 89 44 24 2b 41 80
4c 24 30 04 4c 8d 64 24 68 48 89 ee 4c 89 e7 e8 3d 48 fe
[ 405.952396] RSP: 0018:88802ea0f838 EFLAGS: 00010246
[ 405.955368] RAX: RBX: 111005d41f08 RCX: dc00
[ 405.958669] RDX: 1110254cc878 RSI: 88802000 RDI: 88812a6643c0
[ 405.961980] RBP: 88812a664000 R08: R09:
[ 405.965319] R10: 88802ea0fd00 R11: R12:
[ 405.968624] R13: 0041 R14: 88802b836800 R15: 8881250570c0
[ 405.971989] FS: () GS:888055a0()
knlGS:
[ 405.975645] CS: 0010 DS: ES: CR0: 80050033
[ 405.978755] CR2: 0030 CR3: 2d20 CR4: 00340ee0
[ 405.982150] Call Trace:
[ 405.984768] ? amp_read_loc_assoc+0x170/0x170 [bluetooth]
[ 405.987875] ? rcu_read_unlock+0x50/0x50
[ 405.990663] ? deref_stack_reg+0xf0/0xf0
[ 405.993403] ? __module_address+0x3f/0x370
[ 405.996184] ? hci_cmd_work+0x180/0x330 [bluetooth]
[ 405.999170] ? hci_conn_hash_lookup_handle+0x1a1/0x270 [bluetooth]
[ 406.002354] hci_event_packet+0x1476/0x7e00 [bluetooth]
[ 406.005407] ? arch_stack_walk+0x8f/0xf0
[ 406.008206] ? ret_from_fork+0x27/0x50
[ 406.010887] ? hci_cmd_complete_evt+0xbf70/0xbf70 [bluetooth]
[ 406.013933] ? stack_trace_save+0x8a/0xb0
[ 406.016618] ? do_profile_hits.isra.4.cold.9+0x2d/0x2d
[ 406.019483] ? lock_acquire+0x1a3/0x970
[ 406.022092] ? __wake_up_common_lock+0xaf/0x130
I didn't found any solution upstream. After the vmcore analysis I found what is
wrong. And took reference from the following patch, which seems to be on the
similar line
commit 6dfccd13db2ff2b709ef60a50163925d477549aa
Author: Anmol Karn
Date: Wed Sep 30 19:48:13 2020 +0530
Bluetooth: Fix null pointer dereference in hci_event_packet()
AMP_MGR is getting derefernced in hci_phy_link_complete_evt(), when
called
from hci_event_packet() and there is a possibility, that hcon->amp_mgr
may
not be found when accessing after initialization of hcon.
- net/bluetooth/hci_event.c:4945
How we can avoid this scenario. So I made the chages and tested. It worked or
avoided the kernel panic. But I really don't know that some one has already
posted the patch. I would have love to backport the patch, I was more of
looking for the fix. That's where I didn't applied the reported-by tag as I
thought it reported internal only.
Thanks & regards,
Gopal Tiwari
- Original Message -
From: "Dmitry Vyukov"
To: "Peilin Ye"
Cc: "Marcel Holtmann" , "Johan Hedberg"
, "Andrei Emeltchenko" ,
"Greg Kroah-Hartman" , "David S. Miller"
, "Jakub Kicinski" ,
linux-kernel-ment...@lists.linuxfoundation.org, "syzkaller-bugs"
, "linux-bluetooth"
, "netdev" , "LKML"
, gtiw...@redhat.com,
syzbot+f4fb0eaafdb51c32a...@syzkaller.appspotmail.com
Sent: Wednesday, March 3, 2021 1:51:41 PM
Subject: Re: [Linux-kernel-mentees] [PATCH net] Bluetooth: Fix NULL pointer
dereference in amp_read_loc_assoc_final_data()
On Sat, Aug 8, 2020 at 6:06 AM Peilin Ye wrote:
>
> Prevent amp_read_loc_assoc_final_data() from dereferencing `mgr` as NULL.
>
> Reported-and-tested-by: syzbot+f4fb0eaafdb51c32a...@syzkaller.appspotmail.com
> Fixes: 9495b2ee757f ("Bluetooth: AMP: Process Chan Selected event")
> Signed-off-by: Peilin Ye
> ---
> net/bluetooth/amp.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/net/bluetooth/amp.c b/net/bluetooth/amp.c
> index 9c711f0dfae3..be2d469d6369 100644
> --- a/net/bluetooth/amp.c
> +++ b/net/bluetooth/amp.c
> @@ -297,6 +297,9 @@ void amp_read_loc_assoc_final_data(struct hci_dev *hdev,
> struct hci_request req;
> int err;
>
> + if (!mgr)
> + return;
> +
> cp.phy_handle = hcon->handle;
> cp.len_so_far = cpu_to_le16(0);
> cp.max_len = cpu_to_le16(hdev->amp_assoc_size);
Not sure what happened here, but the merged patch somehow has a
different author and no Reported-by tag:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e8bd76ede155fd54d8c41d045dda43cd3174d506
so let's tell syzbot what fixed it manually:
#syz fix:
Bluetooth: Fix null pointer dereference in amp_read_loc_assoc_final_data
Re: [Linux-kernel-mentees] [PATCH net] Bluetooth: Fix NULL pointer dereference in amp_read_loc_assoc_final_data()
On Sat, Aug 8, 2020 at 6:06 AM Peilin Ye wrote:
>
> Prevent amp_read_loc_assoc_final_data() from dereferencing `mgr` as NULL.
>
> Reported-and-tested-by: syzbot+f4fb0eaafdb51c32a...@syzkaller.appspotmail.com
> Fixes: 9495b2ee757f ("Bluetooth: AMP: Process Chan Selected event")
> Signed-off-by: Peilin Ye
> ---
> net/bluetooth/amp.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/net/bluetooth/amp.c b/net/bluetooth/amp.c
> index 9c711f0dfae3..be2d469d6369 100644
> --- a/net/bluetooth/amp.c
> +++ b/net/bluetooth/amp.c
> @@ -297,6 +297,9 @@ void amp_read_loc_assoc_final_data(struct hci_dev *hdev,
> struct hci_request req;
> int err;
>
> + if (!mgr)
> + return;
> +
> cp.phy_handle = hcon->handle;
> cp.len_so_far = cpu_to_le16(0);
> cp.max_len = cpu_to_le16(hdev->amp_assoc_size);
Not sure what happened here, but the merged patch somehow has a
different author and no Reported-by tag:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e8bd76ede155fd54d8c41d045dda43cd3174d506
so let's tell syzbot what fixed it manually:
#syz fix:
Bluetooth: Fix null pointer dereference in amp_read_loc_assoc_final_data
[Linux-kernel-mentees] [PATCH net] Bluetooth: Fix NULL pointer dereference in amp_read_loc_assoc_final_data()
Prevent amp_read_loc_assoc_final_data() from dereferencing `mgr` as NULL.
Reported-and-tested-by: syzbot+f4fb0eaafdb51c32a...@syzkaller.appspotmail.com
Fixes: 9495b2ee757f ("Bluetooth: AMP: Process Chan Selected event")
Signed-off-by: Peilin Ye
---
net/bluetooth/amp.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/bluetooth/amp.c b/net/bluetooth/amp.c
index 9c711f0dfae3..be2d469d6369 100644
--- a/net/bluetooth/amp.c
+++ b/net/bluetooth/amp.c
@@ -297,6 +297,9 @@ void amp_read_loc_assoc_final_data(struct hci_dev *hdev,
struct hci_request req;
int err;
+ if (!mgr)
+ return;
+
cp.phy_handle = hcon->handle;
cp.len_so_far = cpu_to_le16(0);
cp.max_len = cpu_to_le16(hdev->amp_assoc_size);
--
2.25.1
