5.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ian Abbott abbotti@mev.co.uk
[ 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/staging/comedi/comedi_fops.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
--- a/drivers/staging/comedi/comedi_fops.c +++ b/drivers/staging/comedi/comedi_fops.c @@ -1607,6 +1607,16 @@ error: 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 @@ -2261,6 +2271,9 @@ static long comedi_unlocked_ioctl(struct 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; @@ -3112,6 +3125,9 @@ static int compat_insnlist(struct file * 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;