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* [PATCH 5.10.y] comedi: Fix initialization of data for instructions that write to subdevice
@ 2025-07-24 18:16 Ian Abbott
  2025-07-25 23:26 ` Sasha Levin
  0 siblings, 1 reply; 4+ messages in thread
From: Ian Abbott @ 2025-07-24 18:16 UTC (permalink / raw)
  To: stable; +Cc: Ian Abbott, Greg Kroah-Hartman

[ 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


^ permalink raw reply related	[flat|nested] 4+ messages in thread
* [PATCH 5.10.y] comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large
@ 2025-07-24 18:12 Ian Abbott
  2025-07-24 18:12 ` [PATCH 5.10.y] comedi: Fix initialization of data for instructions that write to subdevice Ian Abbott
  0 siblings, 1 reply; 4+ messages in thread
From: Ian Abbott @ 2025-07-24 18:12 UTC (permalink / raw)
  To: stable; +Cc: Ian Abbott, syzbot+d6995b62e5ac7d79557a, Greg Kroah-Hartman

[ 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


^ permalink raw reply related	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2025-07-26  0:24 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2025-07-24 18:16 [PATCH 5.10.y] comedi: Fix initialization of data for instructions that write to subdevice Ian Abbott
2025-07-25 23:26 ` Sasha Levin
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2025-07-24 18:12 [PATCH 5.10.y] comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large Ian Abbott
2025-07-24 18:12 ` [PATCH 5.10.y] comedi: Fix initialization of data for instructions that write to subdevice Ian Abbott
2025-07-26  0:24   ` Sasha Levin

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