Re: [RFC PATCH] hw/net/e1000e: Do not abort() on invalid PSRCTL register value

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

[-- Attachment #1: Type: text/plain, Size: 4945 bytes --]

Le ven. 29 mai 2020 08:36, Jason Wang <jasowang@redhat.com> a écrit :

>
> On 2020/5/25 下午8:23, Philippe Mathieu-Daudé wrote:
> > libFuzzer found using 'qemu-system-i386 -M q35':
> >
> > qemu: hardware error: e1000e: PSRCTL.BSIZE0 cannot be zero
> > CPU #0:
> > EAX=00000000 EBX=00000000 ECX=00000000 EDX=00000663
> > ESI=00000000 EDI=00000000 EBP=00000000 ESP=00000000
> > EIP=0000fff0 EFL=00000002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
> > ES =0000 00000000 0000ffff 00009300
> > CS =f000 ffff0000 0000ffff 00009b00
> > SS =0000 00000000 0000ffff 00009300
> > DS =0000 00000000 0000ffff 00009300
> > FS =0000 00000000 0000ffff 00009300
> > GS =0000 00000000 0000ffff 00009300
> > LDT=0000 00000000 0000ffff 00008200
> > TR =0000 00000000 0000ffff 00008b00
> > GDT=     00000000 0000ffff
> > IDT=     00000000 0000ffff
> > CR0=60000010 CR2=00000000 CR3=00000000 CR4=00000000
> > DR0=00000000 DR1=00000000 DR2=00000000 DR3=00000000
> > DR6=ffff0ff0 DR7=00000400
> > EFER=0000000000000000
> > FCW=037f FSW=0000 [ST=0] FTW=00 MXCSR=00001f80
> > FPR0=0000000000000000 0000 FPR1=0000000000000000 0000
> > FPR2=0000000000000000 0000 FPR3=0000000000000000 0000
> > FPR4=0000000000000000 0000 FPR5=0000000000000000 0000
> > FPR6=0000000000000000 0000 FPR7=0000000000000000 0000
> > XMM00=00000000000000000000000000000000
> XMM01=00000000000000000000000000000000
> > XMM02=00000000000000000000000000000000
> XMM03=00000000000000000000000000000000
> > XMM04=00000000000000000000000000000000
> XMM05=00000000000000000000000000000000
> > XMM06=00000000000000000000000000000000
> XMM07=00000000000000000000000000000000
> > ==1988== ERROR: libFuzzer: deadly signal
> >      #6 0x7fae4d3ea894 in __GI_abort (/lib64/libc.so.6+0x22894)
> >      #7 0x563f4cc59a1d in hw_error (qemu-fuzz-i386+0xe8ca1d)
> >      #8 0x563f4d7c93f2 in e1000e_set_psrctl (qemu-fuzz-i386+0x19fc3f2)
> >      #9 0x563f4d7b798f in e1000e_core_write (qemu-fuzz-i386+0x19ea98f)
> >      #10 0x563f4d7afc46 in e1000e_mmio_write (qemu-fuzz-i386+0x19e2c46)
> >      #11 0x563f4cc9a0a7 in memory_region_write_accessor
> (qemu-fuzz-i386+0xecd0a7)
> >      #12 0x563f4cc99c13 in access_with_adjusted_size
> (qemu-fuzz-i386+0xeccc13)
> >      #13 0x563f4cc987b4 in memory_region_dispatch_write
> (qemu-fuzz-i386+0xecb7b4)
> >
> > It simply sent the following 2 I/O command to the e1000e
> > PCI BAR #2 I/O region:
> >
> >    writew 0x0100 0x0c00 # RCTL =   E1000_RCTL_DTYP_MASK
> >    writeb 0x2170 0x00   # PSRCTL = 0
> >
> > 2813 static void
> > 2814 e1000e_set_psrctl(E1000ECore *core, int index, uint32_t val)
> > 2815 {
> > 2816     if (core->mac[RCTL] & E1000_RCTL_DTYP_MASK) {
> > 2817
> > 2818         if ((val & E1000_PSRCTL_BSIZE0_MASK) == 0) {
> > 2819             hw_error("e1000e: PSRCTL.BSIZE0 cannot be zero");
> > 2820         }
> >
> > Instead of calling hw_error() which abort the process (it is
> > meant for CPU fatal error condition, not for device logging),
> > log the invalid request with qemu_log_mask(LOG_GUEST_ERROR)
> > and return ignoring the request.
>

Maybe more understandable adding a comma after "return":

"... and return, ignoring the request."

>
> > Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> > ---
> > RFC because there might be something clever than returning...
> > Probably worth a Cc:qemu-stable@ tag
>
>
> I can't think of a better solution here. And the code looks safe if we
> accept zero value.
>
> So I applied this patch.
>

Thanks. Can you append the "Cc:qemu-stable@..." tag please?


> Thanks
>
>
> > ---
> >   hw/net/e1000e_core.c | 10 +++++++---
> >   1 file changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/hw/net/e1000e_core.c b/hw/net/e1000e_core.c
> > index d5676871fa..bcd186cac5 100644
> > --- a/hw/net/e1000e_core.c
> > +++ b/hw/net/e1000e_core.c
> > @@ -34,9 +34,9 @@
> >   */
> >
> >   #include "qemu/osdep.h"
> > +#include "qemu/log.h"
> >   #include "net/net.h"
> >   #include "net/tap.h"
> > -#include "hw/hw.h"
> >   #include "hw/pci/msi.h"
> >   #include "hw/pci/msix.h"
> >   #include "sysemu/runstate.h"
> > @@ -2816,11 +2816,15 @@ e1000e_set_psrctl(E1000ECore *core, int index,
> uint32_t val)
> >       if (core->mac[RCTL] & E1000_RCTL_DTYP_MASK) {
> >
> >           if ((val & E1000_PSRCTL_BSIZE0_MASK) == 0) {
> > -            hw_error("e1000e: PSRCTL.BSIZE0 cannot be zero");
> > +            qemu_log_mask(LOG_GUEST_ERROR,
> > +                          "e1000e: PSRCTL.BSIZE0 cannot be zero");
> > +            return;
> >           }
> >
> >           if ((val & E1000_PSRCTL_BSIZE1_MASK) == 0) {
> > -            hw_error("e1000e: PSRCTL.BSIZE1 cannot be zero");
> > +            qemu_log_mask(LOG_GUEST_ERROR,
> > +                          "e1000e: PSRCTL.BSIZE1 cannot be zero");
> > +            return;
> >           }
> >       }
> >
>
>

[-- Attachment #2: Type: text/html, Size: 6924 bytes --]