[PATCH 5.10.y] comedi: Fix initialization of data for instructions that write to subdevice

[PATCH 5.10.y] comedi: Fix initialization of data for instructions that write to subdevice

[Ian Abbott]

[ Upstream commit 46d8c744136ce2454aa4c35c138cc06817f92b8e ]

Some Comedi subdevice instruction handlers are known to access
instruction data elements beyond the first `insn->n` elements in some
cases.  The `do_insn_ioctl()` and `do_insnlist_ioctl()` functions
allocate at least `MIN_SAMPLES` (16) data elements to deal with this,
but they do not initialize all of that.  For Comedi instruction codes
that write to the subdevice, the first `insn->n` data elements are
copied from user-space, but the remaining elements are left
uninitialized.  That could be a problem if the subdevice instruction
handler reads the uninitialized data.  Ensure that the first
`MIN_SAMPLES` elements are initialized before calling these instruction
handlers, filling the uncopied elements with 0.  For
`do_insnlist_ioctl()`, the same data buffer elements are used for
handling a list of instructions, so ensure the first `MIN_SAMPLES`
elements are initialized for each instruction that writes to the
subdevice.

Fixes: ed9eccbe8970 ("Staging: add comedi core")
Cc: stable@vger.kernel.org # 5.13+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20250707161439.88385-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/staging/comedi/comedi_fops.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index 5aa6a84d1fa6..96d68cc8f449 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -1551,21 +1551,27 @@ static int do_insnlist_ioctl(struct comedi_device *dev,
 	}
 
 	for (i = 0; i < n_insns; ++i) {
+		unsigned int n = insns[i].n;
+
 		if (insns[i].insn & INSN_MASK_WRITE) {
 			if (copy_from_user(data, insns[i].data,
-					   insns[i].n * sizeof(unsigned int))) {
+					   n * sizeof(unsigned int))) {
 				dev_dbg(dev->class_dev,
 					"copy_from_user failed\n");
 				ret = -EFAULT;
 				goto error;
 			}
+			if (n < MIN_SAMPLES) {
+				memset(&data[n], 0, (MIN_SAMPLES - n) *
+						    sizeof(unsigned int));
+			}
 		}
 		ret = parse_insn(dev, insns + i, data, file);
 		if (ret < 0)
 			goto error;
 		if (insns[i].insn & INSN_MASK_READ) {
 			if (copy_to_user(insns[i].data, data,
-					 insns[i].n * sizeof(unsigned int))) {
+					 n * sizeof(unsigned int))) {
 				dev_dbg(dev->class_dev,
 					"copy_to_user failed\n");
 				ret = -EFAULT;
@@ -1638,6 +1644,10 @@ static int do_insn_ioctl(struct comedi_device *dev,
 			ret = -EFAULT;
 			goto error;
 		}
+		if (insn->n < MIN_SAMPLES) {
+			memset(&data[insn->n], 0,
+			       (MIN_SAMPLES - insn->n) * sizeof(unsigned int));
+		}
 	}
 	ret = parse_insn(dev, insn, data, file);
 	if (ret < 0)
-- 
2.47.2

[PATCH 5.10.y] comedi: Fix initialization of data for instructions that write to subdevice

[Ian Abbott]

[ Upstream commit 46d8c744136ce2454aa4c35c138cc06817f92b8e ]

Some Comedi subdevice instruction handlers are known to access
instruction data elements beyond the first `insn->n` elements in some
cases.  The `do_insn_ioctl()` and `do_insnlist_ioctl()` functions
allocate at least `MIN_SAMPLES` (16) data elements to deal with this,
but they do not initialize all of that.  For Comedi instruction codes
that write to the subdevice, the first `insn->n` data elements are
copied from user-space, but the remaining elements are left
uninitialized.  That could be a problem if the subdevice instruction
handler reads the uninitialized data.  Ensure that the first
`MIN_SAMPLES` elements are initialized before calling these instruction
handlers, filling the uncopied elements with 0.  For
`do_insnlist_ioctl()`, the same data buffer elements are used for
handling a list of instructions, so ensure the first `MIN_SAMPLES`
elements are initialized for each instruction that writes to the
subdevice.

Fixes: ed9eccbe8970 ("Staging: add comedi core")
Cc: stable@vger.kernel.org # 5.13+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20250707161439.88385-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/staging/comedi/comedi_fops.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index 5aa6a84d1fa6..96d68cc8f449 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -1551,21 +1551,27 @@ static int do_insnlist_ioctl(struct comedi_device *dev,
 	}
 
 	for (i = 0; i < n_insns; ++i) {
+		unsigned int n = insns[i].n;
+
 		if (insns[i].insn & INSN_MASK_WRITE) {
 			if (copy_from_user(data, insns[i].data,
-					   insns[i].n * sizeof(unsigned int))) {
+					   n * sizeof(unsigned int))) {
 				dev_dbg(dev->class_dev,
 					"copy_from_user failed\n");
 				ret = -EFAULT;
 				goto error;
 			}
+			if (n < MIN_SAMPLES) {
+				memset(&data[n], 0, (MIN_SAMPLES - n) *
+						    sizeof(unsigned int));
+			}
 		}
 		ret = parse_insn(dev, insns + i, data, file);
 		if (ret < 0)
 			goto error;
 		if (insns[i].insn & INSN_MASK_READ) {
 			if (copy_to_user(insns[i].data, data,
-					 insns[i].n * sizeof(unsigned int))) {
+					 n * sizeof(unsigned int))) {
 				dev_dbg(dev->class_dev,
 					"copy_to_user failed\n");
 				ret = -EFAULT;
@@ -1638,6 +1644,10 @@ static int do_insn_ioctl(struct comedi_device *dev,
 			ret = -EFAULT;
 			goto error;
 		}
+		if (insn->n < MIN_SAMPLES) {
+			memset(&data[insn->n], 0,
+			       (MIN_SAMPLES - insn->n) * sizeof(unsigned int));
+		}
 	}
 	ret = parse_insn(dev, insn, data, file);
 	if (ret < 0)
-- 
2.47.2

Re: [PATCH 5.10.y] comedi: Fix initialization of data for instructions that write to subdevice

[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: 46d8c744136ce2454aa4c35c138cc06817f92b8e

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:  46d8c744136c ! 1:  9ed5216f103b comedi: Fix initialization of data for instructions that write to subdevice
    @@ Metadata
      ## Commit message ##
         comedi: Fix initialization of data for instructions that write to subdevice
     
    +    [ Upstream commit 46d8c744136ce2454aa4c35c138cc06817f92b8e ]
    +
         Some Comedi subdevice instruction handlers are known to access
         instruction data elements beyond the first `insn->n` elements in some
         cases.  The `do_insn_ioctl()` and `do_insnlist_ioctl()` functions
    @@ Commit message
         Link: https://lore.kernel.org/r/20250707161439.88385-1-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,
      	}
      
      	for (i = 0; i < n_insns; ++i) {
    @@ drivers/comedi/comedi_fops.c: static int do_insnlist_ioctl(struct comedi_device
      				dev_dbg(dev->class_dev,
      					"copy_to_user failed\n");
      				ret = -EFAULT;
    -@@ drivers/comedi/comedi_fops.c: static int do_insn_ioctl(struct comedi_device *dev,
    +@@ drivers/staging/comedi/comedi_fops.c: static int do_insn_ioctl(struct comedi_device *dev,
      			ret = -EFAULT;
      			goto error;
      		}

---

Results of testing on various branches:

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

Re: [PATCH 5.10.y] comedi: Fix initialization of data for instructions that write to subdevice

[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: 46d8c744136ce2454aa4c35c138cc06817f92b8e

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:  46d8c744136c ! 1:  b96c24925413 comedi: Fix initialization of data for instructions that write to subdevice
    @@ Metadata
      ## Commit message ##
         comedi: Fix initialization of data for instructions that write to subdevice
     
    +    [ Upstream commit 46d8c744136ce2454aa4c35c138cc06817f92b8e ]
    +
         Some Comedi subdevice instruction handlers are known to access
         instruction data elements beyond the first `insn->n` elements in some
         cases.  The `do_insn_ioctl()` and `do_insnlist_ioctl()` functions
    @@ Commit message
         Link: https://lore.kernel.org/r/20250707161439.88385-1-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,
      	}
      
      	for (i = 0; i < n_insns; ++i) {
    @@ drivers/comedi/comedi_fops.c: static int do_insnlist_ioctl(struct comedi_device
      				dev_dbg(dev->class_dev,
      					"copy_to_user failed\n");
      				ret = -EFAULT;
    -@@ drivers/comedi/comedi_fops.c: static int do_insn_ioctl(struct comedi_device *dev,
    +@@ drivers/staging/comedi/comedi_fops.c: static int do_insn_ioctl(struct comedi_device *dev,
      			ret = -EFAULT;
      			goto error;
      		}

---

Results of testing on various branches:

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