On Tue, Apr 9, 2019 at 10:59 PM Markus Armbruster <arm...@redhat.com> wrote: > > Philippe Mathieu-Daudé <phi...@redhat.com> writes: > > > On 4/10/19 7:28 AM, Markus Armbruster wrote: > >> Philippe Mathieu-Daudé <phi...@redhat.com> writes: > >>> On 4/9/19 7:40 PM, Markus Armbruster wrote: > >>>> If the value of get_image_size() exceeds INT_MAX / 2 - 10000, the > >>>> computation of @dt_size overflows to a negative number, which then > >>>> gets converted to a very large size_t for g_malloc0() and > >>>> load_image_size(). In the (fortunately improbable) case g_malloc0() > >>>> succeeds and load_image_size() survives, we'd assign the negative > >>>> number to *sizep. What that would do to the callers I can't say, but > >>>> it's unlikely to be good. > >>>> > >>>> Fix by rejecting images whose size would overflow. > >>>> > >>>> Signed-off-by: Markus Armbruster <arm...@redhat.com> > >>>> --- > >>>> device_tree.c | 4 ++++ > >>>> 1 file changed, 4 insertions(+) > >>>> > >>>> diff --git a/device_tree.c b/device_tree.c > >>>> index 296278e12a..f8b46b3c73 100644 > >>>> --- a/device_tree.c > >>>> +++ b/device_tree.c > >>>> @@ -84,6 +84,10 @@ void *load_device_tree(const char *filename_path, int > >>>> *sizep) > >>>> filename_path); > >>>> goto fail; > >>>> } > >>>> + if (dt_size > INT_MAX / 2 - 10000) { > >>> > >>> We should avoid magic number duplication. > >>> That said, this patch looks safe. > >>> > >>> Reviewed-by: Philippe Mathieu-Daudé <phi...@redhat.com> > >> > >> Thanks! > >> > >>> BTW how did you figure that out? > >> > >> Downstream handling of upstream commit da885fe1ee8 led me to the > >> function. I spotted dt_size = get_image_size(filename_path). > >> Experience has taught me to check the left hand side's type. Bad. Then > >> I saw how dt_size gets increased. Worse. > > > > So you genuinely neglected to mention Kurtis Miller then :) > > Explanation, not excuse: the only occurence of the name in my downstream > reading was a two-liner BZ comment, which I totally missed in my haste > to give the fix a chance to make 4.0. I certainly didn't mean to > deprive him of credit!
No worries. I have sent the pull request and it includes the reported by. Alistair > > [...] >