On 04/18/16 at 09:37am, Russell King - ARM Linux wrote: > On Mon, Apr 18, 2016 at 01:35:34PM +0800, Baoquan He wrote: > > On 04/14/16 at 09:00pm, Russell King wrote: > > > Ensure that user memory sizes do not wrap around when validating the > > > user input, which can lead to the following input validation working > > > incorrectly. > > > > > > Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk> > > > --- > > > kernel/kexec_core.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c > > > index 8d34308ea449..d719a4d0ef55 100644 > > > --- a/kernel/kexec_core.c > > > +++ b/kernel/kexec_core.c > > > @@ -169,6 +169,8 @@ int sanity_check_segment_list(struct kimage *image) > > > > > > mstart = image->segment[i].mem; > > > mend = mstart + image->segment[i].memsz; > > > + if (mstart > mend) > > > + return result; > > > > These segments are built in kexec utility, their availability should be > > guaranteed there. If without some alignment handling, wrapping around > > might not happen here. But I don't have strong objection to it. > > In which case, what's the point of all the other validation which is done, > like the check below: > > > > if ((mstart & ~PAGE_MASK) || (mend & ~PAGE_MASK)) > > > return result; > > > if (mend >= KEXEC_DESTINATION_MEMORY_LIMIT) > > Your reply is contradictory to the whole suite of tests which kexec does > to validate its input from userspace. It's not contradictory. In kexec utility it will call valid_memory_segment() to check each segment. And there it will check if the start is bigger than end. What I meant is if start is 5000, end is 5100, an alignment of end will make start> end case happen. Anyway I am fine with this check adding, the safer, the better. > > -- > RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/ > FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up > according to speedtest.net. > > _______________________________________________ > kexec mailing list > kexec at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec
