Re: [PATCH v2] hw/acpi/erst.c: Fix memory handling issues

[Alexander Bulekov]

On 221024 1224, Alexander Bulekov wrote:
> On 221024 1742, Christian A. Ehrhardt wrote:
> > - Fix memset argument order: The second argument is
> >   the value, the length goes last.
> > - Fix an integer overflow reported by Alexander Bulekov.
> > 
> > Both issues allow the guest to overrun the host buffer
> > allocated for the ERST memory device.
> > 
> > Cc: Eric DeVolder <eric.devolder@oracle.com
> > Cc: Alexander Bulekov <alxndr@bu.edu>
> > Cc: qemu-stable@nongnu.org
> > Fixes: f7e26ffa590 ("ACPI ERST: support for ACPI ERST feature")
> > Tested-by: Alexander Bulekov <alxndr@bu.edu>
> 

Also:
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1268

> Reviewed-by: Alexander Bulekov <alxndr@bu.edu>
> 
> > Signed-off-by: Christian A. Ehrhardt <lk@c--e.de>
> > ---
> >  hw/acpi/erst.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/hw/acpi/erst.c b/hw/acpi/erst.c
> > index df856b2669..aefcc03ad6 100644
> > --- a/hw/acpi/erst.c
> > +++ b/hw/acpi/erst.c
> > @@ -635,7 +635,7 @@ static unsigned read_erst_record(ERSTDeviceState *s)
> >          if (record_length < UEFI_CPER_RECORD_MIN_SIZE) {
> >              rc = STATUS_FAILED;
> >          }
> > -        if ((s->record_offset + record_length) > exchange_length) {
> > +        if (record_length > exchange_length - s->record_offset) {
> >              rc = STATUS_FAILED;
> >          }
> >          /* If all is ok, copy the record to the exchange buffer */
> > @@ -684,7 +684,7 @@ static unsigned write_erst_record(ERSTDeviceState *s)
> >      if (record_length < UEFI_CPER_RECORD_MIN_SIZE) {
> >          return STATUS_FAILED;
> >      }
> > -    if ((s->record_offset + record_length) > exchange_length) {
> > +    if (record_length > exchange_length - s->record_offset) {
> >          return STATUS_FAILED;
> >      }
> >  
> > @@ -716,7 +716,7 @@ static unsigned write_erst_record(ERSTDeviceState *s)
> >      if (nvram) {
> >          /* Write the record into the slot */
> >          memcpy(nvram, exchange, record_length);
> > -        memset(nvram + record_length, exchange_length - record_length, 
> > 0xFF);
> > +        memset(nvram + record_length, 0xFF, exchange_length - 
> > record_length);
> >          /* If a new record, increment the record_count */
> >          if (!record_found) {
> >              uint32_t record_count;
> > -- 
> > 2.34.1
> > 
> >