| Message ID | 20210919133727.44694-1-len.baker@gmx.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | ALSA: usx2y: Prefer struct_size over open coded arithmetic | expand |
On Sun, 19 Sep 2021 15:37:27 +0200, Len Baker wrote: > > As noted in the "Deprecated Interfaces, Language Features, Attributes, > and Conventions" documentation [1], size calculations (especially > multiplication) should not be performed in memory allocator (or similar) > function arguments due to the risk of them overflowing. This could lead > to values wrapping around and a smaller allocation being made than the > caller was expecting. Using those allocations could lead to linear > overflows of heap memory and other misbehaviors. > > In this case this is not actually dynamic size: all the operands > involved in the calculation are constant values. However it is better to > refactor this anyway, just to keep the open-coded math idiom out of > code. > > So, use the struct_size() helper to do the arithmetic instead of the > argument "size + size * count" in the kzalloc() function. > > Also, take the opportunity to refactor the declaration variables to make > it more easy to read. > > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments > > Signed-off-by: Len Baker <len.baker@gmx.com> Thanks, applied. Takashi
diff --git a/sound/usb/usx2y/usbusx2yaudio.c b/sound/usb/usx2y/usbusx2yaudio.c index c39cc6851e2d..cfc1ea53978d 100644 --- a/sound/usb/usx2y/usbusx2yaudio.c +++ b/sound/usb/usx2y/usbusx2yaudio.c @@ -668,14 +668,15 @@ static void i_usx2y_04int(struct urb *urb) static int usx2y_rate_set(struct usx2ydev *usx2y, int rate) { - int err = 0, i; - struct snd_usx2y_urb_seq *us = NULL; - int *usbdata = NULL; - const struct s_c2 *ra = rate == 48000 ? setrate_48000 : setrate_44100; + int err = 0, i; + struct snd_usx2y_urb_seq *us = NULL; + int *usbdata = NULL; + const struct s_c2 *ra = rate == 48000 ? setrate_48000 : setrate_44100; struct urb *urb; if (usx2y->rate != rate) { - us = kzalloc(sizeof(*us) + sizeof(struct urb *) * NOOF_SETRATE_URBS, GFP_KERNEL); + us = kzalloc(struct_size(us, urb, NOOF_SETRATE_URBS), + GFP_KERNEL); if (!us) { err = -ENOMEM; goto cleanup;
As noted in the "Deprecated Interfaces, Language Features, Attributes, and Conventions" documentation [1], size calculations (especially multiplication) should not be performed in memory allocator (or similar) function arguments due to the risk of them overflowing. This could lead to values wrapping around and a smaller allocation being made than the caller was expecting. Using those allocations could lead to linear overflows of heap memory and other misbehaviors. In this case this is not actually dynamic size: all the operands involved in the calculation are constant values. However it is better to refactor this anyway, just to keep the open-coded math idiom out of code. So, use the struct_size() helper to do the arithmetic instead of the argument "size + size * count" in the kzalloc() function. Also, take the opportunity to refactor the declaration variables to make it more easy to read. [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments Signed-off-by: Len Baker <len.baker@gmx.com> --- sound/usb/usx2y/usbusx2yaudio.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) -- 2.25.1