diff options
| author | Ian Abbott <abbotti@mev.co.uk> | 2025-07-04 13:04:05 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-07-24 08:56:28 +0200 |
| commit | 992d600f284e719242a434166e86c1999649b71c (patch) | |
| tree | 2077d2e1a361591161c27996de5b41b9e5a33713 | |
| parent | 3eab654f5d199ecd45403c6588cda63e491fcfca (diff) | |
comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large
commit 08ae4b20f5e82101d77326ecab9089e110f224cc upstream.
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>
| -rw-r--r-- | drivers/comedi/comedi_fops.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/drivers/comedi/comedi_fops.c b/drivers/comedi/comedi_fops.c index b9df9b19d4bd..b588618d03d8 100644 --- a/drivers/comedi/comedi_fops.c +++ b/drivers/comedi/comedi_fops.c @@ -1589,6 +1589,16 @@ 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 @@ -2239,6 +2249,9 @@ 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; @@ -3090,6 +3103,9 @@ 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; |