> -----Original Message-----
> From: Siddh Raman Pant <code@xxxxxxxx>
> Sent: Thursday, August 25, 2022 6:01 AM
> To: palmer@xxxxxxxxxxxx
> Cc: davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; johan.hedberg@xxxxxxxxx;
> kuba@xxxxxxxxxx; linux-bluetooth@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; linux@xxxxxxxxxxxx; luiz.dentz@xxxxxxxxx;
> marcel@xxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; pabeni@xxxxxxxxxx
> Subject: Re: [PATCH] Bluetooth: L2CAP: Elide a string overflow warning
>
> On Fri, 12 Aug 2022 11:22:49 +0530 Palmer Dabbelt wrote:
> > From: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
> >
> > Without this I get a string op warning related to copying from a
> > possibly NULL pointer. I think the warning is spurious, but it's
> > tripping up allmodconfig.
>
> I think it is not spurious, and is due to the following commit:
> d0be8347c623 ("Bluetooth: L2CAP: Fix use-after-free caused by l2cap_chan_put")
That commit was OK - it added an "if (!c) continue" to handle if
the value c is changed to NULL.
> The following commit fixes a similar problem (added the NULL check on line
> 1996):
> 332f1795ca20 ("Bluetooth: L2CAP: Fix l2cap_global_chan_by_psm regression")
That commit wiped out the "if (!c) continue" path escape clause
from the previous patch, introducing a path back to code that
doesn't check for NULL:
- if (!c)
- continue;
-
- read_unlock(&chan_list_lock);
- return c;
+ if (c) {
+ read_unlock(&chan_list_lock);
+ return c;
+ }
}
src_any = !bacmp(&c->src, BDADDR_ANY);
dst_any = !bacmp(&c->dst, BDADDR_ANY);
> > inlined from 'l2cap_global_chan_by_psm' at /scratch/merges/ko-linux-
> next/linux/net/bluetooth/l2cap_core.c:2003:15:
> > /scratch/merges/ko-linux-next/linux/include/linux/fortify-string.h:44:33:
> error: '__builtin_memcmp' specified bound 6 exceeds source size 0 [-
> Werror=stringop-overread]
> > 44 | #define __underlying_memcmp __builtin_memcmp
> > | ^
> > /scratch/merges/ko-linux-next/linux/include/linux/fortify-string.h:420:16:
> note: in expansion of macro '__underlying_memcmp'
> > 420 | return __underlying_memcmp(p, q, size);
> > | ^~~~~~~~~~~~~~~~~~~
> > In function 'memcmp',
> > inlined from 'bacmp' at /scratch/merges/ko-linux-
> next/linux/include/net/bluetooth/bluetooth.h:347:9,
> > inlined from 'l2cap_global_chan_by_psm' at /scratch/merges/ko-linux-
...
> >
> > Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
>
> Tested-by: Siddh Raman Pant <code@xxxxxxxx>
This patch is necessary to get a successful cross-compile of 6.0-rc3
allmodconfig for ARCH=mips on x86.
Tested-by: Robert Elliott <elliott@xxxxxxx>
I suggest you label this patch as:
Fixes: 332f1795ca20 ("Bluetooth: L2CAP: Fix l2cap_global_chan_by_psm regression")
> > ---
> > net/bluetooth/l2cap_core.c | 12 +++++++-----
> > 1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> > index cbe0cae73434..be7f47e52119 100644
> > --- a/net/bluetooth/l2cap_core.c
> > +++ b/net/bluetooth/l2cap_core.c
> > @@ -2000,11 +2000,13 @@ static struct l2cap_chan
> *l2cap_global_chan_by_psm(int state, __le16 psm,
> > }
> >
> > /* Closest match */
> > - src_any = !bacmp(&c->src, BDADDR_ANY);
> > - dst_any = !bacmp(&c->dst, BDADDR_ANY);
> > - if ((src_match && dst_any) || (src_any && dst_match) ||
> > - (src_any && dst_any))
> > - c1 = c;
> > + if (c) {
> > + src_any = !bacmp(&c->src, BDADDR_ANY);
> > + dst_any = !bacmp(&c->dst, BDADDR_ANY);
> > + if ((src_match && dst_any) || (src_any &&
> dst_match) ||
> > + (src_any && dst_any))
> > + c1 = c;
> > + }
> > }
> > }
> >
>
