[ 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;
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.
[ 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 |
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Ian Abbott -
Sasha Levin