| Message ID | 20200526075042.420162-1-ppandit@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] exec: set map length to zero when returning NULL | expand |
On 5/26/20 9:50 AM, P J P wrote: > From: Prasad J Pandit <pjp@fedoraproject.org> > > When mapping physical memory into host's virtual address space, > 'address_space_map' may return NULL if BounceBuffer is in_use. > Set and return '*plen = 0' to avoid later NULL pointer dereference. > > Reported-by: Alexander Bulekov <alxndr@bu.edu> > Fixes: https://bugs.launchpad.net/qemu/+bug/1878259 > Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org> > --- > exec.c | 1 + > 1 file changed, 1 insertion(+) > > Update v3: set *plen = 0; > -> https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg06249.html > > diff --git a/exec.c b/exec.c > index 5162f0d12f..4eea84bf66 100644 > --- a/exec.c > +++ b/exec.c > @@ -3538,6 +3538,7 @@ void *address_space_map(AddressSpace *as, > > if (!memory_access_is_direct(mr, is_write)) { > if (atomic_xchg(&bounce.in_use, true)) { > + *plen = 0; > return NULL; > } > /* Avoid unbounded allocations */ > Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
On Tue, May 26, 2020 at 9:53 AM P J P <ppandit@redhat.com> wrote: > > From: Prasad J Pandit <pjp@fedoraproject.org> > > When mapping physical memory into host's virtual address space, > 'address_space_map' may return NULL if BounceBuffer is in_use. > Set and return '*plen = 0' to avoid later NULL pointer dereference. > > Reported-by: Alexander Bulekov <alxndr@bu.edu> Suggested-by: Paolo Bonzini <pbonzini@redhat.com> > Fixes: https://bugs.launchpad.net/qemu/+bug/1878259 > Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org> > --- > exec.c | 1 + > 1 file changed, 1 insertion(+) > > Update v3: set *plen = 0; > -> https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg06249.html > > diff --git a/exec.c b/exec.c > index 5162f0d12f..4eea84bf66 100644 > --- a/exec.c > +++ b/exec.c > @@ -3538,6 +3538,7 @@ void *address_space_map(AddressSpace *as, > > if (!memory_access_is_direct(mr, is_write)) { > if (atomic_xchg(&bounce.in_use, true)) { > + *plen = 0; > return NULL; > } > /* Avoid unbounded allocations */ > -- > 2.26.2 >
On Tue, 26 May 2020 at 08:53, P J P <ppandit@redhat.com> wrote: > > From: Prasad J Pandit <pjp@fedoraproject.org> > > When mapping physical memory into host's virtual address space, > 'address_space_map' may return NULL if BounceBuffer is in_use. > Set and return '*plen = 0' to avoid later NULL pointer dereference. > > Reported-by: Alexander Bulekov <alxndr@bu.edu> > Fixes: https://bugs.launchpad.net/qemu/+bug/1878259 > Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org> The doc comment for this function in include/exec/memory.h currently says "May return %NULL if resources needed to perform the mapping are exhausted." If we're tightening the API to guarantee to also set *plen to 0 in this failure case it would be good to capture that in the documentation, eg: "May return %NULL (and set *@plen to 0) if resources needed to perform the mapping are exhausted.)" thanks -- PMM
+-- On Tue, 26 May 2020, Peter Maydell wrote --+ | The doc comment for this function in include/exec/memory.h currently says | | "May return %NULL if resources needed to perform the mapping | are exhausted." | | If we're tightening the API to guarantee to also set *plen to 0 in this | failure case it would be good to capture that in the documentation, eg: | | "May return %NULL (and set *@plen to 0) if resources needed | to perform the mapping are exhausted.)" Sending patch v4. Thank you. -- Prasad J Pandit / Red Hat Product Security Team 8685 545E B54C 486B C6EB 271E E285 8B5A F050 DE8D
diff --git a/exec.c b/exec.c index 5162f0d12f..4eea84bf66 100644 --- a/exec.c +++ b/exec.c @@ -3538,6 +3538,7 @@ void *address_space_map(AddressSpace *as, if (!memory_access_is_direct(mr, is_write)) { if (atomic_xchg(&bounce.in_use, true)) { + *plen = 0; return NULL; } /* Avoid unbounded allocations */