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[PATCH] nfc: pn533: Fix null-ptr-deref in pn533_recv_frame()

Yuxuan Hu posted 1 patch 1 year, 9 months ago 
drivers/nfc/pn533/pn533.c | 4 ++++
1 file changed, 4 insertions(+)
[PATCH] nfc: pn533: Fix null-ptr-deref in pn533_recv_frame()
Posted by Yuxuan Hu 1 year, 9 months ago 
From: Yuxuan Hu <yuxuanhu@buaa.edu.cn>

Our fuzzing tool found a null-ptr-deref in function pn533_recv_frame 
(/drivers/nfc/pn533/pn533.c) in kernel 6.8.

(1.1) When execute the NFC_CMD_START_POLL command via netlink, the 
pn533_send_cmd_async function (/drivers/nfc/pn533/pn533.c: 1714) is 
called, which sends the PN533_CMD_IN_AUTOPOLL command packet.

(2.1) If a pn533 response frame that does not match the command is 
received, the following call sequence is executed:
pn533_recv_frame (/drivers/nfc/pn533/pn533.c: 2165)
    pn533_rx_frame_is_cmd_response (/drivers/nfc/pn533/pn533.c: 2194)
    pn533_wq_cmd_complete (/drivers/nfc/pn533/pn533.c: 2022)
        pn533_send_async_complete (/drivers/nfc/pn533/pn533.c: 547)
            pn533_autopoll_complete (/drivers/nfc/pn533/pn533.c: 414)

(2.2) After completing (2.1), dev->cmd is freed and set to null 
(/drivers/nfc/pn533/pn533.c: 432-433).

(3.1) If another incorrect pn533 response frame is received during 
the above process, (2.1) and (2.2) will be executed concurrently, and 
the initial process setting dev->cmd to null causes the concurrent 
process to trigger a null-ptr-deref in pn533_recv_frame.

Although pn533_recv_frame checks for dev->cmd at the beginning, it is 
possible that dev->cmd is set to null after the check.

Through our verification, this concurrent vulnerability has a high 
probability of occurrence and needs to be fixed.

Kernel print messages when null-ptr-deref is triggered (including PN533 
packets, PN533 module errors, and KASAN reports) are as follows.
We added printk of the data packets, and printk before the relevant steps 
in pn533_send_async_complete and pn533_recv_frame.

  -> 00 00 FF 08 F8 D4 60 FF 03 00 11 12 04 A3 00 
  <- 00 00 FF 00 FF 00 
  <- 00 00 FF 0E F2 D5 86 01 10 09 01 00 20 08 04 9B 2C EE 9F 0A 00 
  tty tty60: NFC: It it not the response to the last command
  arted polling nfc device
  <- 00 00 FF 03 FD D5 41 00 EA 00 
  tty tty60: NFC: pn533_autopoll_complete  autopoll complete error -5
  tty tty60: NFC: It it not the response to the last command
  tty tty60: NFC: Error -5 when running autopoll
  tty tty60: NFC: autopoll operation has been stopped
  pn533_send_async_complete: set dev->cmd to null!!!
  pn533_recv_frame: dev->cmd is null!!!
  BUG: kernel NULL pointer dereference, address: 0000000000000014
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0 
  Oops: 0002 [#1] PREEMPT SMP KASAN PTI
  CPU: 0 PID: 5541 Comm: kworker/0:0 Tainted: G           O       6.8.0 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
  Workqueue: events nfcvirt_recv_work [nfcvirt]
  RIP: 0010:pn533_recv_frame+0x18a/0x1e0 [pn533]
  Code: 43 ff ff ff 48 8b bb 80 02 00 00 48 c7 c6 0b 02 46 c0 31 c0 e8 97 64 4f c4 48 83 bb b0 01 00 00 00 74 3f 48 8b 83 b0 01 00 00 <c7> 40 14 fb ff ff ff 48 8b 83 b0 01 00 00 48 85 c0 0f 85 3b ff ff
  RSP: 0018:ffff88802665fc68 EFLAGS: 00010246
  RAX: 0000000000000000 RBX: ffff88804a13b800 RCX: ad381de3b3cd5e00
  RDX: 1ffff11004ccbf38 RSI: 0000000000000008 RDI: ffff88802665f9e0
  RBP: ffff88804fb25000 R08: ffff88802665f9e7 R09: 1ffff11004ccbf3c
  R10: dffffc0000000000 R11: ffffed1004ccbf3d R12: 0000000000001950
  R13: ffff88804ab80000 R14: ffff888021d22640 R15: ffff88802665fcb0
  FS:  0000000000000000(0000) GS:ffff88806d200000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000000000014 CR3: 0000000004ebc000 CR4: 00000000000006f0
  Call Trace:
   <TASK>
   ? __die_body+0x62/0xb0
   ? page_fault_oops+0x421/0x740
   ? kernelmode_fixup_or_oops+0x1d0/0x1d0
   ? asan.module_ctor+0x10/0x10
   ? vprintk_emit+0x3f0/0x3f0
   ? kernelmode_fixup_or_oops+0x163/0x1d0
   ? do_user_addr_fault+0xb6c/0xde0
   ? irq_work_queue+0x54/0xa0
   ? do_kern_addr_fault+0x160/0x160
   ? __call_rcu_common+0x518/0xc30
   ? _dev_err+0x106/0x150
   ? exc_page_fault+0x66/0x1a0
   ? asm_exc_page_fault+0x22/0x30
   ? pn533_recv_frame+0x18a/0x1e0 [pn533]
   ? pn533_recv_frame+0x1d7/0x1e0 [pn533]
   nfcvirt_recv_work+0x24e/0x320 [nfcvirt]
   ? wake_bit_function+0x230/0x230
   process_one_work+0x4f0/0xab0
   worker_thread+0x8af/0xee0
   ? process_one_work+0xab0/0xab0
   kthread+0x275/0x300
   ? process_one_work+0xab0/0xab0
   ? kthread_blkcg+0xa0/0xa0
   ret_from_fork+0x30/0x60
   ? kthread_blkcg+0xa0/0xa0
   ret_from_fork_asm+0x11/0x20
   </TASK>
  Modules linked in: nfcvirt(O) pn533(O) nfc(O) ki_coverage(O) [last unloaded: pn533(O)]
  CR2: 0000000000000014
  ---[ end trace 0000000000000000 ]---
  RIP: 0010:pn533_recv_frame+0x18a/0x1e0 [pn533]
  Code: 43 ff ff ff 48 8b bb 80 02 00 00 48 c7 c6 0b 02 46 c0 31 c0 e8 97 64 4f c4 48 83 bb b0 01 00 00 00 74 3f 48 8b 83 b0 01 00 00 <c7> 40 14 fb ff ff ff 48 8b 83 b0 01 00 00 48 85 c0 0f 85 3b ff ff
  RSP: 0018:ffff88802665fc68 EFLAGS: 00010246
  RAX: 0000000000000000 RBX: ffff88804a13b800 RCX: ad381de3b3cd5e00
  RDX: 1ffff11004ccbf38 RSI: 0000000000000008 RDI: ffff88802665f9e0
  RBP: ffff88804fb25000 R08: ffff88802665f9e7 R09: 1ffff11004ccbf3c
  R10: dffffc0000000000 R11: ffffed1004ccbf3d R12: 0000000000001950
  R13: ffff88804ab80000 R14: ffff888021d22640 R15: ffff88802665fcb0
  FS:  0000000000000000(0000) GS:ffff88806d200000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000000000014 CR3: 0000000004ebc000 CR4: 00000000000006f0

Signed-off-by: Yuxuan Hu <yuxuanhu@buaa.edu.cn>
---
 drivers/nfc/pn533/pn533.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/nfc/pn533/pn533.c b/drivers/nfc/pn533/pn533.c
index b19c39dcfbd9..a80a23332f59 100644
--- a/drivers/nfc/pn533/pn533.c
+++ b/drivers/nfc/pn533/pn533.c
@@ -2190,9 +2190,13 @@ void pn533_recv_frame(struct pn533 *dev, struct sk_buff *skb, int status)
 
 	if (!dev->ops->rx_is_frame_valid(skb->data, dev)) {
 		nfc_err(dev->dev, "Received an invalid frame\n");
+		if (!dev->cmd)
+			goto sched_wq;
 		dev->cmd->status = -EIO;
 	} else if (!pn533_rx_frame_is_cmd_response(dev, skb->data)) {
 		nfc_err(dev->dev, "It it not the response to the last command\n");
+		if (!dev->cmd)
+			goto sched_wq;
 		dev->cmd->status = -EIO;
 	}
 
-- 
2.25.1
Re: [PATCH] nfc: pn533: Fix null-ptr-deref in pn533_recv_frame()
Posted by Markus Elfring 1 year, 9 months ago 
> Our fuzzing tool found a null-ptr-deref in function pn533_recv_frame
> (/drivers/nfc/pn533/pn533.c) in kernel 6.8.
…

Can it be nicer to use the term “null pointer dereference” for the commit message here?

Regards,
Markus
Re: [PATCH] nfc: pn533: Fix null-ptr-deref in pn533_recv_frame()
Posted by Krzysztof Kozlowski 1 year, 9 months ago 
On 22/04/2024 10:04, Yuxuan Hu wrote:
>    ? kthread_blkcg+0xa0/0xa0
>    ret_from_fork_asm+0x11/0x20
>    </TASK>
>   Modules linked in: nfcvirt(O) pn533(O) nfc(O) ki_coverage(O) [last unloaded: pn533(O)]
>   CR2: 0000000000000014
>   ---[ end trace 0000000000000000 ]---
>   RIP: 0010:pn533_recv_frame+0x18a/0x1e0 [pn533]
>   Code: 43 ff ff ff 48 8b bb 80 02 00 00 48 c7 c6 0b 02 46 c0 31 c0 e8 97 64 4f c4 48 83 bb b0 01 00 00 00 74 3f 48 8b 83 b0 01 00 00 <c7> 40 14 fb ff ff ff 48 8b 83 b0 01 00 00 48 85 c0 0f 85 3b ff ff
>   RSP: 0018:ffff88802665fc68 EFLAGS: 00010246
>   RAX: 0000000000000000 RBX: ffff88804a13b800 RCX: ad381de3b3cd5e00
>   RDX: 1ffff11004ccbf38 RSI: 0000000000000008 RDI: ffff88802665f9e0
>   RBP: ffff88804fb25000 R08: ffff88802665f9e7 R09: 1ffff11004ccbf3c
>   R10: dffffc0000000000 R11: ffffed1004ccbf3d R12: 0000000000001950
>   R13: ffff88804ab80000 R14: ffff888021d22640 R15: ffff88802665fcb0
>   FS:  0000000000000000(0000) GS:ffff88806d200000(0000) knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   CR2: 0000000000000014 CR3: 0000000004ebc000 CR4: 00000000000006f0
> 
> Signed-off-by: Yuxuan Hu <yuxuanhu@buaa.edu.cn>

Also, please provide here Fixes, Cc:stable and Closes tags.

Best regards,
Krzysztof
Re: [PATCH] nfc: pn533: Fix null-ptr-deref in pn533_recv_frame()
Posted by Krzysztof Kozlowski 1 year, 9 months ago 
On 22/04/2024 10:04, Yuxuan Hu wrote:
> From: Yuxuan Hu <yuxuanhu@buaa.edu.cn>
> 
> Our fuzzing tool found a null-ptr-deref in function pn533_recv_frame 
> (/drivers/nfc/pn533/pn533.c) in kernel 6.8.
> 
> (1.1) When execute the NFC_CMD_START_POLL command via netlink, the 
> pn533_send_cmd_async function (/drivers/nfc/pn533/pn533.c: 1714) is 
> called, which sends the PN533_CMD_IN_AUTOPOLL command packet.
> 
> (2.1) If a pn533 response frame that does not match the command is 
> received, the following call sequence is executed:
> pn533_recv_frame (/drivers/nfc/pn533/pn533.c: 2165)
>     pn533_rx_frame_is_cmd_response (/drivers/nfc/pn533/pn533.c: 2194)
>     pn533_wq_cmd_complete (/drivers/nfc/pn533/pn533.c: 2022)
>         pn533_send_async_complete (/drivers/nfc/pn533/pn533.c: 547)
>             pn533_autopoll_complete (/drivers/nfc/pn533/pn533.c: 414)
> 
> (2.2) After completing (2.1), dev->cmd is freed and set to null 
> (/drivers/nfc/pn533/pn533.c: 432-433).
> 
> (3.1) If another incorrect pn533 response frame is received during 
> the above process, (2.1) and (2.2) will be executed concurrently, and 
> the initial process setting dev->cmd to null causes the concurrent 
> process to trigger a null-ptr-deref in pn533_recv_frame.
> 
> Although pn533_recv_frame checks for dev->cmd at the beginning, it is 
> possible that dev->cmd is set to null after the check.

That sounds reasonable... but solution does not.

> 
> Through our verification, this concurrent vulnerability has a high 
> probability of occurrence and needs to be fixed.
> 
> Kernel print messages when null-ptr-deref is triggered (including PN533 
> packets, PN533 module errors, and KASAN reports) are as follows.
> We added printk of the data packets, and printk before the relevant steps 
> in pn533_send_async_complete and pn533_recv_frame.
> 
>   -> 00 00 FF 08 F8 D4 60 FF 03 00 11 12 04 A3 00 
>   <- 00 00 FF 00 FF 00 
>   <- 00 00 FF 0E F2 D5 86 01 10 09 01 00 20 08 04 9B 2C EE 9F 0A 00 
>   tty tty60: NFC: It it not the response to the last command
>   arted polling nfc device
>   <- 00 00 FF 03 FD D5 41 00 EA 00 
>   tty tty60: NFC: pn533_autopoll_complete  autopoll complete error -5
>   tty tty60: NFC: It it not the response to the last command
>   tty tty60: NFC: Error -5 when running autopoll
>   tty tty60: NFC: autopoll operation has been stopped
>   pn533_send_async_complete: set dev->cmd to null!!!
>   pn533_recv_frame: dev->cmd is null!!!
>   BUG: kernel NULL pointer dereference, address: 0000000000000014
>   #PF: supervisor write access in kernel mode
>   #PF: error_code(0x0002) - not-present page
>   PGD 0 P4D 0 
>   Oops: 0002 [#1] PREEMPT SMP KASAN PTI
>   CPU: 0 PID: 5541 Comm: kworker/0:0 Tainted: G           O       6.8.0 #1
>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
>   Workqueue: events nfcvirt_recv_work [nfcvirt]
>   RIP: 0010:pn533_recv_frame+0x18a/0x1e0 [pn533]
>   Code: 43 ff ff ff 48 8b bb 80 02 00 00 48 c7 c6 0b 02 46 c0 31 c0 e8 97 64 4f c4 48 83 bb b0 01 00 00 00 74 3f 48 8b 83 b0 01 00 00 <c7> 40 14 fb ff ff ff 48 8b 83 b0 01 00 00 48 85 c0 0f 85 3b ff ff
>   RSP: 0018:ffff88802665fc68 EFLAGS: 00010246
>   RAX: 0000000000000000 RBX: ffff88804a13b800 RCX: ad381de3b3cd5e00
>   RDX: 1ffff11004ccbf38 RSI: 0000000000000008 RDI: ffff88802665f9e0
>   RBP: ffff88804fb25000 R08: ffff88802665f9e7 R09: 1ffff11004ccbf3c
>   R10: dffffc0000000000 R11: ffffed1004ccbf3d R12: 0000000000001950
>   R13: ffff88804ab80000 R14: ffff888021d22640 R15: ffff88802665fcb0
>   FS:  0000000000000000(0000) GS:ffff88806d200000(0000) knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   CR2: 0000000000000014 CR3: 0000000004ebc000 CR4: 00000000000006f0

Please trim the log from irrelevant register dumps.

>   Call Trace:
>    <TASK>
>    ? __die_body+0x62/0xb0
>    ? page_fault_oops+0x421/0x740
>    ? kernelmode_fixup_or_oops+0x1d0/0x1d0
>    ? asan.module_ctor+0x10/0x10
>    ? vprintk_emit+0x3f0/0x3f0
>    ? kernelmode_fixup_or_oops+0x163/0x1d0
>    ? do_user_addr_fault+0xb6c/0xde0
>    ? irq_work_queue+0x54/0xa0
>    ? do_kern_addr_fault+0x160/0x160
>    ? __call_rcu_common+0x518/0xc30
>    ? _dev_err+0x106/0x150
>    ? exc_page_fault+0x66/0x1a0
>    ? asm_exc_page_fault+0x22/0x30
>    ? pn533_recv_frame+0x18a/0x1e0 [pn533]
>    ? pn533_recv_frame+0x1d7/0x1e0 [pn533]
>    nfcvirt_recv_work+0x24e/0x320 [nfcvirt]
>    ? wake_bit_function+0x230/0x230
>    process_one_work+0x4f0/0xab0
>    worker_thread+0x8af/0xee0
>    ? process_one_work+0xab0/0xab0
>    kthread+0x275/0x300
>    ? process_one_work+0xab0/0xab0
>    ? kthread_blkcg+0xa0/0xa0
>    ret_from_fork+0x30/0x60
>    ? kthread_blkcg+0xa0/0xa0
>    ret_from_fork_asm+0x11/0x20
>    </TASK>
>   Modules linked in: nfcvirt(O) pn533(O) nfc(O) ki_coverage(O) [last unloaded: pn533(O)]
>   CR2: 0000000000000014
>   ---[ end trace 0000000000000000 ]---
>   RIP: 0010:pn533_recv_frame+0x18a/0x1e0 [pn533]
>   Code: 43 ff ff ff 48 8b bb 80 02 00 00 48 c7 c6 0b 02 46 c0 31 c0 e8 97 64 4f c4 48 83 bb b0 01 00 00 00 74 3f 48 8b 83 b0 01 00 00 <c7> 40 14 fb ff ff ff 48 8b 83 b0 01 00 00 48 85 c0 0f 85 3b ff ff
>   RSP: 0018:ffff88802665fc68 EFLAGS: 00010246
>   RAX: 0000000000000000 RBX: ffff88804a13b800 RCX: ad381de3b3cd5e00
>   RDX: 1ffff11004ccbf38 RSI: 0000000000000008 RDI: ffff88802665f9e0
>   RBP: ffff88804fb25000 R08: ffff88802665f9e7 R09: 1ffff11004ccbf3c
>   R10: dffffc0000000000 R11: ffffed1004ccbf3d R12: 0000000000001950
>   R13: ffff88804ab80000 R14: ffff888021d22640 R15: ffff88802665fcb0
>   FS:  0000000000000000(0000) GS:ffff88806d200000(0000) knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   CR2: 0000000000000014 CR3: 0000000004ebc000 CR4: 00000000000006f0

Same here.

This just makes the commit log less readable.

> 
> Signed-off-by: Yuxuan Hu <yuxuanhu@buaa.edu.cn>
> ---
>  drivers/nfc/pn533/pn533.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/nfc/pn533/pn533.c b/drivers/nfc/pn533/pn533.c
> index b19c39dcfbd9..a80a23332f59 100644
> --- a/drivers/nfc/pn533/pn533.c
> +++ b/drivers/nfc/pn533/pn533.c
> @@ -2190,9 +2190,13 @@ void pn533_recv_frame(struct pn533 *dev, struct sk_buff *skb, int status)
>  
>  	if (!dev->ops->rx_is_frame_valid(skb->data, dev)) {
>  		nfc_err(dev->dev, "Received an invalid frame\n");

Imagine here dev->cmd != NULL...

> +		if (!dev->cmd)
> +			goto sched_wq;

... but here is being NULL-ified by pn533_send_async_complete(). How
does your solution prevent anything? I assume pn533_recv_frame() will be
executed in parallel to the workqueue.

A bit better solution would be to NULL-ify dev->cmd at the beginning of
pn533_send_async_complete(), because that seems logical. The complete
callback takes ownership of dev->cmd, so why it performs the assignment
at the end?

However even above code will keep the race open for short period.
Probably some locking would solve it or checking for dev->cmd in few
places with barriers.

Best regards,
Krzysztof
Re: [PATCH] nfc: pn533: Fix null-ptr-deref in pn533_recv_frame()
Posted by Yuxuan-Hu 1 year, 9 months ago 
Hi Krzysztof,
Thanks for your reply.

On 2024/4/24 13:36, Krzysztof Kozlowski wrote:
> A bit better solution would be to NULL-ify dev->cmd at the beginning of
> pn533_send_async_complete(), because that seems logical. The complete
> callback takes ownership of dev->cmd, so why it performs the assignment
> at the end?
>
> However even above code will keep the race open for short period.
> Probably some locking would solve it or checking for dev->cmd in few
> places with barriers.
>
> Best regards,
> Krzysztof

I think adding a lock seems to be a better solution, however, acquire a 
lock on each access to dev->cmd does not seem to be an appropriate 
implementation.
I wonder whether you think it is appropriate to acquire a lock at the 
beginning of pn533_recv_frame(), and release it when 
pn533_wq_cmd_complete() is finished, thus ensuring that another work 
will not start when one pn533_wq_cmd_complete() work is not yet finished.

Best regards,
Yuxuan
Re: [PATCH] nfc: pn533: Fix null-ptr-deref in pn533_recv_frame()
Posted by Krzysztof Kozlowski 1 year, 9 months ago 
On 24/04/2024 16:00, Yuxuan-Hu wrote:
> Hi Krzysztof,
> Thanks for your reply.
> 
> On 2024/4/24 13:36, Krzysztof Kozlowski wrote:
>> A bit better solution would be to NULL-ify dev->cmd at the beginning of
>> pn533_send_async_complete(), because that seems logical. The complete
>> callback takes ownership of dev->cmd, so why it performs the assignment
>> at the end?
>>
>> However even above code will keep the race open for short period.
>> Probably some locking would solve it or checking for dev->cmd in few
>> places with barriers.
>>
>> Best regards,
>> Krzysztof
> 
> I think adding a lock seems to be a better solution, however, acquire a 
> lock on each access to dev->cmd does not seem to be an appropriate 
> implementation.
> I wonder whether you think it is appropriate to acquire a lock at the 
> beginning of pn533_recv_frame(), and release it when 
> pn533_wq_cmd_complete() is finished, thus ensuring that another work 
> will not start when one pn533_wq_cmd_complete() work is not yet finished.

I don't know this driver well enough, but it currently does not have any
locking around this so it assumes pn533_recv_frame() cannot start
concurrently, before complete callback finishes.

This could be solved, if it makes sense.

However maybe it would be enough to take:
1. Move contents of dev->cmd to another member in dev (e.g.
dev->cmd_in_progress), first checking if that member is empty (then
maybe wait? or return -EBUSY?)
2. dev->cmd = NULL
3. queue_work (see also explanation of barriers there)
4. The cmd_complete_work workqueue takes ownership of
dev->cmd_in_progress and NULL-ifies it at end of work + barrier.

Best regards,
Krzysztof

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