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[88.10.102.251]) by smtp.gmail.com with ESMTPSA id p9sm8899921wru.61.2019.08.13.03.31.45 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Tue, 13 Aug 2019 03:31:45 -0700 (PDT) To: P J P References: <20190809063835.6717-1-ppandit@redhat.com> <20190809063835.6717-2-ppandit@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Openpgp: id=89C1E78F601EE86C867495CBA2A3FD6EDEADC0DE; url=http://pgp.mit.edu/pks/lookup?op=get&search=0xA2A3FD6EDEADC0DE Message-ID: Date: Tue, 13 Aug 2019 12:31:44 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.85.221.67 Subject: Re: [Qemu-devel] [PATCH v3 1/2] scsi: lsi: exit infinite loop while executing script (CVE-2019-12068) 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: Fam Zheng , Marcelo Tosatti , Mark Cave-Ayland , QEMU Developers , Bugs SysSec , Paolo Bonzini , Stefano Garzarella Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Prasad, On 8/13/19 12:05 PM, P J P wrote: > +-- On Fri, 9 Aug 2019, P J P wrote --+ > | From: Prasad J Pandit > | > | When executing script in lsi_execute_script(), the LSI scsi > | adapter emulator advances 's->dsp' index to read next opcode. > | This can lead to an infinite loop if the next opcode is empty. > | Exit such loop after reading 10k empty opcodes. > | > | Reported-by: Bugs SysSec > | Signed-off-by: Prasad J Pandit > | --- > | hw/scsi/lsi53c895a.c | 11 ++++++++++- > | 1 file changed, 10 insertions(+), 1 deletion(-) > | > | Update v3: raise an illegal instruction interrupt and exit > | -> https://lists.gnu.org/archive/html/qemu-devel/2019-08/msg01427.html > | > | diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c > | index 10468c1ec1..e703ef4c9d 100644 > | --- a/hw/scsi/lsi53c895a.c > | +++ b/hw/scsi/lsi53c895a.c > | @@ -185,6 +185,9 @@ static const char *names[] = { > | /* Flag set if this is a tagged command. */ > | #define LSI_TAG_VALID (1 << 16) > | > | +/* Maximum instructions to process. */ > | +#define LSI_MAX_INSN 10000 > | + > | typedef struct lsi_request { > | SCSIRequest *req; > | uint32_t tag; > | @@ -1132,7 +1135,13 @@ static void lsi_execute_script(LSIState *s) > | > | s->istat1 |= LSI_ISTAT1_SRUN; > | again: > | - insn_processed++; > | + if (++insn_processed > LSI_MAX_INSN) { > | + trace_lsi_execute_script_tc_illegal(); > | + lsi_script_dma_interrupt(s, LSI_DSTAT_IID); > | + lsi_disconnect(s); > | + trace_lsi_execute_script_stop(); > | + return; My understanding of Marcelo's explanation (https://lists.gnu.org/archive/html/qemu-devel/2019-08/msg01427.html) is we can kill insn_processed. > | + } > | insn = read_dword(s, s->dsp); > | if (!insn) { > | /* If we receive an empty opcode increment the DSP by 4 bytes > | > > Ping...?! > -- > Prasad J Pandit / Red Hat Product Security Team > 47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F >