* [PATCH] comedi: fix divide-by-zero in comedi_buf_munge()
@ 2025-09-24 1:49 Deepanshu Kartikey
2025-09-24 1:49 ` syzbot
0 siblings, 1 reply; 7+ messages in thread
From: Deepanshu Kartikey @ 2025-09-24 1:49 UTC (permalink / raw)
To: syzbot+f6c3c066162d2c43a66c; +Cc: Deepanshu Kartikey, stable
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
The comedi_buf_munge() function performs a modulo operation
`async->munge_chan %= async->cmd.chanlist_len` without first
checking if chanlist_len is zero. If a user program submits
a command with chanlist_len set to zero, this causes a
divide-by-zero error when the device processes data in the
interrupt handler path.
Add a check for zero chanlist_len at the beginning of the
function, similar to the existing checks for !map and
CMDF_RAWDATA flag. When chanlist_len is zero, update
munge_count and return early, indicating the data was
handled without munging.
This prevents potential kernel panics from malformed user commands.
Reported-by: syzbot+f6c3c066162d2c43a66c@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=f6c3c066162d2c43a66c
Cc: stable@vger.kernel.org
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
drivers/comedi/comedi_buf.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/comedi/comedi_buf.c b/drivers/comedi/comedi_buf.c
index 002c0e76baff..786f888299ce 100644
--- a/drivers/comedi/comedi_buf.c
+++ b/drivers/comedi/comedi_buf.c
@@ -321,6 +321,11 @@ static unsigned int comedi_buf_munge(struct comedi_subdevice *s,
async->munge_count += num_bytes;
return num_bytes;
}
+
+ if (async->cmd.chanlist_len == 0) {
+ async->munge_count += num_bytes;
+ return num_bytes;
+ }
/* don't munge partial samples */
num_bytes -= num_bytes % num_sample_bytes;
--
2.43.0
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH] comedi: fix divide-by-zero in comedi_buf_munge()
2025-09-24 1:49 [PATCH] comedi: fix divide-by-zero in comedi_buf_munge() Deepanshu Kartikey
@ 2025-09-24 1:49 ` syzbot
0 siblings, 0 replies; 7+ messages in thread
From: syzbot @ 2025-09-24 1:49 UTC (permalink / raw)
To: kartikey406; +Cc: kartikey406, stable, linux-kernel, syzkaller-bugs
> #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
This crash does not have a reproducer. I cannot test it.
>
> The comedi_buf_munge() function performs a modulo operation
> `async->munge_chan %= async->cmd.chanlist_len` without first
> checking if chanlist_len is zero. If a user program submits
> a command with chanlist_len set to zero, this causes a
> divide-by-zero error when the device processes data in the
> interrupt handler path.
>
> Add a check for zero chanlist_len at the beginning of the
> function, similar to the existing checks for !map and
> CMDF_RAWDATA flag. When chanlist_len is zero, update
> munge_count and return early, indicating the data was
> handled without munging.
>
> This prevents potential kernel panics from malformed user commands.
>
> Reported-by: syzbot+f6c3c066162d2c43a66c@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=f6c3c066162d2c43a66c
> Cc: stable@vger.kernel.org
> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
> ---
> drivers/comedi/comedi_buf.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/comedi/comedi_buf.c b/drivers/comedi/comedi_buf.c
> index 002c0e76baff..786f888299ce 100644
> --- a/drivers/comedi/comedi_buf.c
> +++ b/drivers/comedi/comedi_buf.c
> @@ -321,6 +321,11 @@ static unsigned int comedi_buf_munge(struct comedi_subdevice *s,
> async->munge_count += num_bytes;
> return num_bytes;
> }
> +
> + if (async->cmd.chanlist_len == 0) {
> + async->munge_count += num_bytes;
> + return num_bytes;
> + }
>
> /* don't munge partial samples */
> num_bytes -= num_bytes % num_sample_bytes;
> --
> 2.43.0
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH] comedi: fix divide-by-zero in comedi_buf_munge()
@ 2025-09-24 1:56 Deepanshu Kartikey
2025-09-24 9:03 ` Ian Abbott
0 siblings, 1 reply; 7+ messages in thread
From: Deepanshu Kartikey @ 2025-09-24 1:56 UTC (permalink / raw)
To: Ian Abbott, H Hartley Sweeten
Cc: Greg Kroah-Hartman, linux-kernel, stable, Deepanshu Kartikey,
syzbot+f6c3c066162d2c43a66c
The comedi_buf_munge() function performs a modulo operation
`async->munge_chan %= async->cmd.chanlist_len` without first
checking if chanlist_len is zero. If a user program submits
a command with chanlist_len set to zero, this causes a
divide-by-zero error when the device processes data in the
interrupt handler path.
Add a check for zero chanlist_len at the beginning of the
function, similar to the existing checks for !map and
CMDF_RAWDATA flag. When chanlist_len is zero, update
munge_count and return early, indicating the data was
handled without munging.
This prevents potential kernel panics from malformed user commands.
Reported-by: syzbot+f6c3c066162d2c43a66c@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=f6c3c066162d2c43a66c
Cc: stable@vger.kernel.org
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
drivers/comedi/comedi_buf.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/comedi/comedi_buf.c b/drivers/comedi/comedi_buf.c
index 002c0e76baff..786f888299ce 100644
--- a/drivers/comedi/comedi_buf.c
+++ b/drivers/comedi/comedi_buf.c
@@ -321,6 +321,11 @@ static unsigned int comedi_buf_munge(struct comedi_subdevice *s,
async->munge_count += num_bytes;
return num_bytes;
}
+
+ if (async->cmd.chanlist_len == 0) {
+ async->munge_count += num_bytes;
+ return num_bytes;
+ }
/* don't munge partial samples */
num_bytes -= num_bytes % num_sample_bytes;
--
2.43.0
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH] comedi: fix divide-by-zero in comedi_buf_munge()
2025-09-24 1:56 Deepanshu Kartikey
@ 2025-09-24 9:03 ` Ian Abbott
0 siblings, 0 replies; 7+ messages in thread
From: Ian Abbott @ 2025-09-24 9:03 UTC (permalink / raw)
To: Deepanshu Kartikey, H Hartley Sweeten
Cc: Greg Kroah-Hartman, linux-kernel, stable,
syzbot+f6c3c066162d2c43a66c
On 24/09/2025 02:56, Deepanshu Kartikey wrote:
> The comedi_buf_munge() function performs a modulo operation
> `async->munge_chan %= async->cmd.chanlist_len` without first
> checking if chanlist_len is zero. If a user program submits
> a command with chanlist_len set to zero, this causes a
> divide-by-zero error when the device processes data in the
> interrupt handler path.
I don't think it should happen for supported hardware devices that are
working properly, but it helps to defend against the unexpected.
> Add a check for zero chanlist_len at the beginning of the
> function, similar to the existing checks for !map and
> CMDF_RAWDATA flag. When chanlist_len is zero, update
> munge_count and return early, indicating the data was
> handled without munging.
>
> This prevents potential kernel panics from malformed user commands.
>
> Reported-by: syzbot+f6c3c066162d2c43a66c@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=f6c3c066162d2c43a66c
> Cc: stable@vger.kernel.org
> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
> ---
> drivers/comedi/comedi_buf.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/comedi/comedi_buf.c b/drivers/comedi/comedi_buf.c
> index 002c0e76baff..786f888299ce 100644
> --- a/drivers/comedi/comedi_buf.c
> +++ b/drivers/comedi/comedi_buf.c
> @@ -321,6 +321,11 @@ static unsigned int comedi_buf_munge(struct comedi_subdevice *s,
> async->munge_count += num_bytes;
> return num_bytes;
> }
> +
> + if (async->cmd.chanlist_len == 0) {
> + async->munge_count += num_bytes;
> + return num_bytes;
> + }
This `if` statement could be merged with the preceding `if` statement
that has the same body, which would save a few lines.
>
> /* don't munge partial samples */
> num_bytes -= num_bytes % num_sample_bytes;
--
-=( Ian Abbott <abbotti@mev.co.uk> || MEV Ltd. is a company )=-
-=( registered in England & Wales. Regd. number: 02862268. )=-
-=( Regd. addr.: S11 & 12 Building 67, Europa Business Park, )=-
-=( Bird Hall Lane, STOCKPORT, SK3 0XA, UK. || www.mev.co.uk )=-
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH] comedi: fix divide-by-zero in comedi_buf_munge()
@ 2025-09-24 1:47 Deepanshu Kartikey
2025-09-24 1:47 ` syzbot
0 siblings, 1 reply; 7+ messages in thread
From: Deepanshu Kartikey @ 2025-09-24 1:47 UTC (permalink / raw)
To: syzbot+f6c3c066162d2c43a66c; +Cc: Deepanshu Kartikey, stable
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
The comedi_buf_munge() function performs a modulo operation
`async->munge_chan %= async->cmd.chanlist_len` without first
checking if chanlist_len is zero. If a user program submits
a command with chanlist_len set to zero, this causes a
divide-by-zero error when the device processes data in the
interrupt handler path.
Add a check for zero chanlist_len at the beginning of the
function, similar to the existing checks for !map and
CMDF_RAWDATA flag. When chanlist_len is zero, update
munge_count and return early, indicating the data was
handled without munging.
This prevents potential kernel panics from malformed user commands.
Reported-by: syzbot+f6c3c066162d2c43a66c@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=f6c3c066162d2c43a66c
Cc: stable@vger.kernel.org
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
drivers/comedi/comedi_buf.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/comedi/comedi_buf.c b/drivers/comedi/comedi_buf.c
index 002c0e76baff..786f888299ce 100644
--- a/drivers/comedi/comedi_buf.c
+++ b/drivers/comedi/comedi_buf.c
@@ -321,6 +321,11 @@ static unsigned int comedi_buf_munge(struct comedi_subdevice *s,
async->munge_count += num_bytes;
return num_bytes;
}
+
+ if (async->cmd.chanlist_len == 0) {
+ async->munge_count += num_bytes;
+ return num_bytes;
+ }
/* don't munge partial samples */
num_bytes -= num_bytes % num_sample_bytes;
--
2.43.0
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH] comedi: fix divide-by-zero in comedi_buf_munge()
2025-09-24 1:47 Deepanshu Kartikey
@ 2025-09-24 1:47 ` syzbot
0 siblings, 0 replies; 7+ messages in thread
From: syzbot @ 2025-09-24 1:47 UTC (permalink / raw)
To: kartikey406; +Cc: kartikey406, stable, linux-kernel, syzkaller-bugs
> #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
This crash does not have a reproducer. I cannot test it.
>
> The comedi_buf_munge() function performs a modulo operation
> `async->munge_chan %= async->cmd.chanlist_len` without first
> checking if chanlist_len is zero. If a user program submits
> a command with chanlist_len set to zero, this causes a
> divide-by-zero error when the device processes data in the
> interrupt handler path.
>
> Add a check for zero chanlist_len at the beginning of the
> function, similar to the existing checks for !map and
> CMDF_RAWDATA flag. When chanlist_len is zero, update
> munge_count and return early, indicating the data was
> handled without munging.
>
> This prevents potential kernel panics from malformed user commands.
>
> Reported-by: syzbot+f6c3c066162d2c43a66c@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=f6c3c066162d2c43a66c
> Cc: stable@vger.kernel.org
> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
> ---
> drivers/comedi/comedi_buf.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/comedi/comedi_buf.c b/drivers/comedi/comedi_buf.c
> index 002c0e76baff..786f888299ce 100644
> --- a/drivers/comedi/comedi_buf.c
> +++ b/drivers/comedi/comedi_buf.c
> @@ -321,6 +321,11 @@ static unsigned int comedi_buf_munge(struct comedi_subdevice *s,
> async->munge_count += num_bytes;
> return num_bytes;
> }
> +
> + if (async->cmd.chanlist_len == 0) {
> + async->munge_count += num_bytes;
> + return num_bytes;
> + }
>
> /* don't munge partial samples */
> num_bytes -= num_bytes % num_sample_bytes;
> --
> 2.43.0
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH] comedi: fix divide-by-zero in comedi_buf_munge()
@ 2025-09-13 6:00 Deepanshu Kartikey
0 siblings, 0 replies; 7+ messages in thread
From: Deepanshu Kartikey @ 2025-09-13 6:00 UTC (permalink / raw)
To: Suhah Khan; +Cc: Deepanshu Kartikey, syzbot+f6c3c066162d2c43a66c, stable
The comedi_buf_munge() function performs a modulo operation
`async->munge_chan %= async->cmd.chanlist_len` without first
checking if chanlist_len is zero. If a user program submits
a command with chanlist_len set to zero, this causes a
divide-by-zero error when the device processes data in the
interrupt handler path.
Add a check for zero chanlist_len at the beginning of the
function, similar to the existing checks for !map and
CMDF_RAWDATA flag. When chanlist_len is zero, update
munge_count and return early, indicating the data was
handled without munging.
This prevents potential kernel panics from malformed user commands.
Reported-by: syzbot+f6c3c066162d2c43a66c@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=f6c3c066162d2c43a66c
Cc: stable@vger.kernel.org
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
drivers/comedi/comedi_buf.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/comedi/comedi_buf.c b/drivers/comedi/comedi_buf.c
index 002c0e76baff..786f888299ce 100644
--- a/drivers/comedi/comedi_buf.c
+++ b/drivers/comedi/comedi_buf.c
@@ -321,6 +321,11 @@ static unsigned int comedi_buf_munge(struct comedi_subdevice *s,
async->munge_count += num_bytes;
return num_bytes;
}
+
+ if (async->cmd.chanlist_len == 0) {
+ async->munge_count += num_bytes;
+ return num_bytes;
+ }
/* don't munge partial samples */
num_bytes -= num_bytes % num_sample_bytes;
--
2.43.0
^ permalink raw reply related [flat|nested] 7+ messages in thread
end of thread, other threads:[~2025-09-24 9:11 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
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2025-09-24 1:49 [PATCH] comedi: fix divide-by-zero in comedi_buf_munge() Deepanshu Kartikey
2025-09-24 1:49 ` syzbot
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2025-09-24 1:56 Deepanshu Kartikey
2025-09-24 9:03 ` Ian Abbott
2025-09-24 1:47 Deepanshu Kartikey
2025-09-24 1:47 ` syzbot
2025-09-13 6:00 Deepanshu Kartikey
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