[PATCH 5.10.y] comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large

[PATCH 5.10.y] comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large

[Ian Abbott]

[ Upstream commit 08ae4b20f5e82101d77326ecab9089e110f224cc ]

The handling of the `COMEDI_INSNLIST` ioctl allocates a kernel buffer to
hold the array of `struct comedi_insn`, getting the length from the
`n_insns` member of the `struct comedi_insnlist` supplied by the user.
The allocation will fail with a WARNING and a stack dump if it is too
large.

Avoid that by failing with an `-EINVAL` error if the supplied `n_insns`
value is unreasonable.

Define the limit on the `n_insns` value in the `MAX_INSNS` macro.  Set
this to the same value as `MAX_SAMPLES` (65536), which is the maximum
allowed sum of the values of the member `n` in the array of `struct
comedi_insn`, and sensible comedi instructions will have an `n` of at
least 1.

Reported-by: syzbot+d6995b62e5ac7d79557a@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d6995b62e5ac7d79557a
Fixes: ed9eccbe8970 ("Staging: add comedi core")
Tested-by: Ian Abbott <abbotti@mev.co.uk>
Cc: stable@vger.kernel.org # 5.13+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20250704120405.83028-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/staging/comedi/comedi_fops.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index 8f896e6208a8..5aa6a84d1fa6 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -1584,6 +1584,16 @@ static int do_insnlist_ioctl(struct comedi_device *dev,
 	return i;
 }
 
+#define MAX_INSNS   MAX_SAMPLES
+static int check_insnlist_len(struct comedi_device *dev, unsigned int n_insns)
+{
+	if (n_insns > MAX_INSNS) {
+		dev_dbg(dev->class_dev, "insnlist length too large\n");
+		return -EINVAL;
+	}
+	return 0;
+}
+
 /*
  * COMEDI_INSN ioctl
  * synchronous instruction
@@ -2234,6 +2244,9 @@ static long comedi_unlocked_ioctl(struct file *file, unsigned int cmd,
 			rc = -EFAULT;
 			break;
 		}
+		rc = check_insnlist_len(dev, insnlist.n_insns);
+		if (rc)
+			break;
 		insns = kcalloc(insnlist.n_insns, sizeof(*insns), GFP_KERNEL);
 		if (!insns) {
 			rc = -ENOMEM;
@@ -3085,6 +3098,9 @@ static int compat_insnlist(struct file *file, unsigned long arg)
 	if (copy_from_user(&insnlist32, compat_ptr(arg), sizeof(insnlist32)))
 		return -EFAULT;
 
+	rc = check_insnlist_len(dev, insnlist32.n_insns);
+	if (rc)
+		return rc;
 	insns = kcalloc(insnlist32.n_insns, sizeof(*insns), GFP_KERNEL);
 	if (!insns)
 		return -ENOMEM;
-- 
2.47.2

[PATCH 5.10.y] comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large

[Ian Abbott]

[ Upstream commit 08ae4b20f5e82101d77326ecab9089e110f224cc ]

The handling of the `COMEDI_INSNLIST` ioctl allocates a kernel buffer to
hold the array of `struct comedi_insn`, getting the length from the
`n_insns` member of the `struct comedi_insnlist` supplied by the user.
The allocation will fail with a WARNING and a stack dump if it is too
large.

Avoid that by failing with an `-EINVAL` error if the supplied `n_insns`
value is unreasonable.

Define the limit on the `n_insns` value in the `MAX_INSNS` macro.  Set
this to the same value as `MAX_SAMPLES` (65536), which is the maximum
allowed sum of the values of the member `n` in the array of `struct
comedi_insn`, and sensible comedi instructions will have an `n` of at
least 1.

Reported-by: syzbot+d6995b62e5ac7d79557a@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d6995b62e5ac7d79557a
Fixes: ed9eccbe8970 ("Staging: add comedi core")
Tested-by: Ian Abbott <abbotti@mev.co.uk>
Cc: stable@vger.kernel.org # 5.13+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20250704120405.83028-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/staging/comedi/comedi_fops.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index 8f896e6208a8..5aa6a84d1fa6 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -1584,6 +1584,16 @@ static int do_insnlist_ioctl(struct comedi_device *dev,
 	return i;
 }
 
+#define MAX_INSNS   MAX_SAMPLES
+static int check_insnlist_len(struct comedi_device *dev, unsigned int n_insns)
+{
+	if (n_insns > MAX_INSNS) {
+		dev_dbg(dev->class_dev, "insnlist length too large\n");
+		return -EINVAL;
+	}
+	return 0;
+}
+
 /*
  * COMEDI_INSN ioctl
  * synchronous instruction
@@ -2234,6 +2244,9 @@ static long comedi_unlocked_ioctl(struct file *file, unsigned int cmd,
 			rc = -EFAULT;
 			break;
 		}
+		rc = check_insnlist_len(dev, insnlist.n_insns);
+		if (rc)
+			break;
 		insns = kcalloc(insnlist.n_insns, sizeof(*insns), GFP_KERNEL);
 		if (!insns) {
 			rc = -ENOMEM;
@@ -3085,6 +3098,9 @@ static int compat_insnlist(struct file *file, unsigned long arg)
 	if (copy_from_user(&insnlist32, compat_ptr(arg), sizeof(insnlist32)))
 		return -EFAULT;
 
+	rc = check_insnlist_len(dev, insnlist32.n_insns);
+	if (rc)
+		return rc;
 	insns = kcalloc(insnlist32.n_insns, sizeof(*insns), GFP_KERNEL);
 	if (!insns)
 		return -ENOMEM;
-- 
2.47.2

Re: [PATCH 5.10.y] comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large

[Ian Abbott]

On 24/07/2025 19:16, Ian Abbott wrote:
> [ Upstream commit 08ae4b20f5e82101d77326ecab9089e110f224cc ]
> 
> The handling of the `COMEDI_INSNLIST` ioctl allocates a kernel buffer to
> hold the array of `struct comedi_insn`, getting the length from the
> `n_insns` member of the `struct comedi_insnlist` supplied by the user.
> The allocation will fail with a WARNING and a stack dump if it is too
> large.
> 
> Avoid that by failing with an `-EINVAL` error if the supplied `n_insns`
> value is unreasonable.
> 
> Define the limit on the `n_insns` value in the `MAX_INSNS` macro.  Set
> this to the same value as `MAX_SAMPLES` (65536), which is the maximum
> allowed sum of the values of the member `n` in the array of `struct
> comedi_insn`, and sensible comedi instructions will have an `n` of at
> least 1.
> 
> Reported-by: syzbot+d6995b62e5ac7d79557a@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=d6995b62e5ac7d79557a
> Fixes: ed9eccbe8970 ("Staging: add comedi core")
> Tested-by: Ian Abbott <abbotti@mev.co.uk>
> Cc: stable@vger.kernel.org # 5.13+
> Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
> Link: https://lore.kernel.org/r/20250704120405.83028-1-abbotti@mev.co.uk
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Apologies for accidentally sending the same set of 9 patches twice!  I 
meant to send a set for 5.10.y, followed by a set for 5.4.y.  Oops.

-- 
-=( 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 )=-

Re: [PATCH 5.10.y] comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: 08ae4b20f5e82101d77326ecab9089e110f224cc

Status in newer kernel trees:
6.15.y | Not found
6.12.y | Not found
6.6.y | Not found
6.1.y | Not found
5.15.y | Not found

Note: The patch differs from the upstream commit:
---
1:  08ae4b20f5e8 ! 1:  4a8bada4e031 comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large
    @@ Metadata
      ## Commit message ##
         comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large
     
    +    [ Upstream commit 08ae4b20f5e82101d77326ecab9089e110f224cc ]
    +
         The handling of the `COMEDI_INSNLIST` ioctl allocates a kernel buffer to
         hold the array of `struct comedi_insn`, getting the length from the
         `n_insns` member of the `struct comedi_insnlist` supplied by the user.
    @@ Commit message
         Link: https://lore.kernel.org/r/20250704120405.83028-1-abbotti@mev.co.uk
         Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
     
    - ## drivers/comedi/comedi_fops.c ##
    -@@ drivers/comedi/comedi_fops.c: static int do_insnlist_ioctl(struct comedi_device *dev,
    + ## drivers/staging/comedi/comedi_fops.c ##
    +@@ drivers/staging/comedi/comedi_fops.c: static int do_insnlist_ioctl(struct comedi_device *dev,
      	return i;
      }
      
    @@ drivers/comedi/comedi_fops.c: static int do_insnlist_ioctl(struct comedi_device
      /*
       * COMEDI_INSN ioctl
       * synchronous instruction
    -@@ drivers/comedi/comedi_fops.c: static long comedi_unlocked_ioctl(struct file *file, unsigned int cmd,
    +@@ drivers/staging/comedi/comedi_fops.c: static long comedi_unlocked_ioctl(struct file *file, unsigned int cmd,
      			rc = -EFAULT;
      			break;
      		}
    @@ drivers/comedi/comedi_fops.c: static long comedi_unlocked_ioctl(struct file *fil
      		insns = kcalloc(insnlist.n_insns, sizeof(*insns), GFP_KERNEL);
      		if (!insns) {
      			rc = -ENOMEM;
    -@@ drivers/comedi/comedi_fops.c: static int compat_insnlist(struct file *file, unsigned long arg)
    +@@ drivers/staging/comedi/comedi_fops.c: static int compat_insnlist(struct file *file, unsigned long arg)
      	if (copy_from_user(&insnlist32, compat_ptr(arg), sizeof(insnlist32)))
      		return -EFAULT;
      

---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| origin/linux-5.10.y       | Success     | Success    |

Re: [PATCH 5.10.y] comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: 08ae4b20f5e82101d77326ecab9089e110f224cc

Status in newer kernel trees:
6.15.y | Not found
6.12.y | Not found
6.6.y | Not found
6.1.y | Not found
5.15.y | Not found

Note: The patch differs from the upstream commit:
---
1:  08ae4b20f5e8 ! 1:  973ce1afed22 comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large
    @@ Metadata
      ## Commit message ##
         comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large
     
    +    [ Upstream commit 08ae4b20f5e82101d77326ecab9089e110f224cc ]
    +
         The handling of the `COMEDI_INSNLIST` ioctl allocates a kernel buffer to
         hold the array of `struct comedi_insn`, getting the length from the
         `n_insns` member of the `struct comedi_insnlist` supplied by the user.
    @@ Commit message
         Link: https://lore.kernel.org/r/20250704120405.83028-1-abbotti@mev.co.uk
         Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
     
    - ## drivers/comedi/comedi_fops.c ##
    -@@ drivers/comedi/comedi_fops.c: static int do_insnlist_ioctl(struct comedi_device *dev,
    + ## drivers/staging/comedi/comedi_fops.c ##
    +@@ drivers/staging/comedi/comedi_fops.c: static int do_insnlist_ioctl(struct comedi_device *dev,
      	return i;
      }
      
    @@ drivers/comedi/comedi_fops.c: static int do_insnlist_ioctl(struct comedi_device
      /*
       * COMEDI_INSN ioctl
       * synchronous instruction
    -@@ drivers/comedi/comedi_fops.c: static long comedi_unlocked_ioctl(struct file *file, unsigned int cmd,
    +@@ drivers/staging/comedi/comedi_fops.c: static long comedi_unlocked_ioctl(struct file *file, unsigned int cmd,
      			rc = -EFAULT;
      			break;
      		}
    @@ drivers/comedi/comedi_fops.c: static long comedi_unlocked_ioctl(struct file *fil
      		insns = kcalloc(insnlist.n_insns, sizeof(*insns), GFP_KERNEL);
      		if (!insns) {
      			rc = -ENOMEM;
    -@@ drivers/comedi/comedi_fops.c: static int compat_insnlist(struct file *file, unsigned long arg)
    +@@ drivers/staging/comedi/comedi_fops.c: static int compat_insnlist(struct file *file, unsigned long arg)
      	if (copy_from_user(&insnlist32, compat_ptr(arg), sizeof(insnlist32)))
      		return -EFAULT;
      

---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| origin/linux-5.10.y       | Success     | Success    |