comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large

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commit 08ae4b20f5 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: ed9eccbe89 ("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>

...

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Ian Abbott 2025-07-04 13:04:05 +01:00 • committed by Greg Kroah-Hartman

parent 73f34d6093

commit 69dc06b951

1 changed files with 16 additions and 0 deletions

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drivers/comedi/comedi_fops.c

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