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Tue, 21 Jul 2020 17:38:25 +0000 (UTC) Subject: Re: [PATCH-for-5.1] hw/ide/ahci: Do not dma_memory_unmap(NULL) To: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , qemu-devel@nongnu.org References: <20200718072854.7001-1-f4bug@amsat.org> From: John Snow Message-ID: Date: Tue, 21 Jul 2020 13:38:25 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200718072854.7001-1-f4bug@amsat.org> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=205.139.110.120; envelope-from=jsnow@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/21 10:58:38 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexander Bulekov , qemu-stable@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 7/18/20 3:28 AM, Philippe Mathieu-Daudé wrote: > libFuzzer triggered the following assertion: > > cat << EOF | qemu-system-i386 -M pc-q35-5.0 \ > -nographic -monitor none -serial none -qtest stdio > outl 0xcf8 0x8000fa24 > outl 0xcfc 0xe1068000 > outl 0xcf8 0x8000fa04 > outw 0xcfc 0x7 > outl 0xcf8 0x8000fb20 > write 0xe1068304 0x1 0x21 > write 0xe1068318 0x1 0x21 > write 0xe1068384 0x1 0x21 > write 0xe1068398 0x2 0x21 > EOF > qemu-system-i386: exec.c:3621: address_space_unmap: Assertion `mr != NULL' failed. > Aborted (core dumped) > > This is because we don't check the return value from dma_memory_map() > which can return NULL, then we call dma_memory_unmap(NULL) which is > illegal. Fix by only unmap if the value is not NULL (and the size is > not the expected one). > > Cc: qemu-stable@nongnu.org > Reported-by: Alexander Bulekov > Fixes: f6ad2e32f8 ("ahci: add ahci emulation") > BugLink: https://bugs.launchpad.net/qemu/+bug/1884693 > Signed-off-by: Philippe Mathieu-Daudé > --- > hw/ide/ahci.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c > index 009120f88b..4f596cb9ce 100644 > --- a/hw/ide/ahci.c > +++ b/hw/ide/ahci.c > @@ -250,7 +250,7 @@ static void map_page(AddressSpace *as, uint8_t **ptr, uint64_t addr, > } > > *ptr = dma_memory_map(as, addr, &len, DMA_DIRECTION_FROM_DEVICE); > - if (len < wanted) { > + if (len < wanted && *ptr) { > dma_memory_unmap(as, *ptr, len, DMA_DIRECTION_FROM_DEVICE, len); > *ptr = NULL; > } > Reviewed-by: John Snow Thanks! this one wound up being easy.