On Wed, Apr 11, 2018 at 4:26 PM, Stephan Müller <smueller@xxxxxxxxxx> wrote: > Hi Dimitry, > > This fix prevents the kernel from crashing when injecting the fault. Good! > Stack traces are yet shown but I guess that is expected every time > a fault is injected. Yes, nothing to fix here. > As to why KASAN did not notice this one, I am not sure. Maybe it is > because I use two buffer pointers to point to (almost) the same memory > (one that is aligned and one pointing to the complete buffer)? After looking at the fix, I figured out what happened with KASAN. Filed https://bugzilla.kernel.org/show_bug.cgi?id=199359. In short, tricky interplay between kzfree, ksize and double-free detection. If KASAN worked as intended it would give a nice "double-free in this stack for object allocated in this stack and previously freed in this stack", which would probably make debugging much simpler. > ---8<--- > > During freeing of the internal buffers used by the DRBG, set the pointer > to NULL. It is possible that the context with the freed buffers is > reused. In case of an error during initialization where the pointers > do not yet point to allocated memory, the NULL value prevents a double > free. > > Signed-off-by: Stephan Mueller <smueller@xxxxxxxxxx> > Reported-by: syzbot+75397ee3df5c70164154@xxxxxxxxxxxxxxxxxxxxxxxxx > --- > crypto/drbg.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/crypto/drbg.c b/crypto/drbg.c > index 4faa2781c964..466a112a4446 100644 > --- a/crypto/drbg.c > +++ b/crypto/drbg.c > @@ -1134,8 +1134,10 @@ static inline void drbg_dealloc_state(struct drbg_state *drbg) > if (!drbg) > return; > kzfree(drbg->Vbuf); > + drbg->Vbuf = NULL; > drbg->V = NULL; > kzfree(drbg->Cbuf); > + drbg->Cbuf = NULL; > drbg->C = NULL; > kzfree(drbg->scratchpadbuf); > drbg->scratchpadbuf = NULL; > -- > 2.14.3 > > > > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/2186798.qrgUIDAn9S%40positron.chronox.de. > For more options, visit https://groups.google.com/d/optout.
