From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52382) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fTlVo-0001zB-Td for qemu-devel@nongnu.org; Fri, 15 Jun 2018 05:59:22 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fTlVn-0007tV-Fe for qemu-devel@nongnu.org; Fri, 15 Jun 2018 05:59:21 -0400 Date: Fri, 15 Jun 2018 11:59:09 +0200 From: Cornelia Huck Message-ID: <20180615115909.1c7df252.cohuck@redhat.com> In-Reply-To: <1529056145-6404-1-git-send-email-thuth@redhat.com> References: <1529056145-6404-1-git-send-email-thuth@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v3] loader: Check access size when calling rom_ptr() to avoid crashes List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Thomas Huth Cc: qemu-devel@nongnu.org, Christian Borntraeger , qemu-s390x@nongnu.org, qemu-arm@nongnu.org, Yongbok Kim , Aurelien Jarno , Mark Cave-Ayland , Artyom Tarasenko , Peter Maydell , Paolo Bonzini , qemu-trivial@nongnu.org On Fri, 15 Jun 2018 11:49:05 +0200 Thomas Huth wrote: > The rom_ptr() function allows direct access to the ROM blobs that we > load during startup. However, there are currently no checks for the > size of the accesses, so it's currently possible to crash QEMU for > example with: > > $ echo "Insane in the mainframe" > /tmp/test.txt > $ s390x-softmmu/qemu-system-s390x -kernel /tmp/test.txt -append xyz > Segmentation fault (core dumped) > $ s390x-softmmu/qemu-system-s390x -kernel /tmp/test.txt -initrd /tmp/test.txt > Segmentation fault (core dumped) > $ echo -n HdrS > /tmp/hdr.txt > $ sparc64-softmmu/qemu-system-sparc64 -kernel /tmp/hdr.txt -initrd /tmp/hdr.txt > Segmentation fault (core dumped) > > We need a possibility to check the size of the ROM area that we want > to access, thus let's add a size parameter to the rom_ptr() function > to avoid these problems. > > Signed-off-by: Thomas Huth > --- > v3: Fix the check in find_rom() > > hw/core/loader.c | 10 +++++----- > hw/mips/mips_malta.c | 6 ++++-- > hw/s390x/ipl.c | 13 ++++++++++--- > hw/sparc/sun4m.c | 4 ++-- > hw/sparc64/sun4u.c | 4 ++-- > include/hw/loader.h | 2 +- > target/arm/cpu.c | 2 +- > 7 files changed, 25 insertions(+), 16 deletions(-) > diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c > index 04245b5..bcac204 100644 > --- a/hw/s390x/ipl.c > +++ b/hw/s390x/ipl.c > @@ -195,8 +199,11 @@ static void s390_ipl_realize(DeviceState *dev, Error **errp) > * we have to overwrite values in the kernel image, > * which are "rom" > */ > - stq_p(rom_ptr(INITRD_PARM_START), initrd_offset); > - stq_p(rom_ptr(INITRD_PARM_SIZE), initrd_size); > + romptr = rom_ptr(INITRD_PARM_START, 16); > + if (romptr) { > + stq_p(romptr, initrd_offset); > + stq_p(romptr + 1, initrd_size); INITRD_PARM_SIZE seems to be unused now. We can remove it in a separate patch if you don't respin, though. > + } > } > } > /* Reviewed-by: Cornelia Huck