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[78.12.252.58]) by smtp.gmail.com with ESMTPSA id u4sm18650194wjz.4.2016.05.20.01.45.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 20 May 2016 01:45:55 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Date: Fri, 20 May 2016 10:45:53 +0200 Message-Id: <1463733953-23850-1-git-send-email-pbonzini@redhat.com> X-Mailer: git-send-email 2.5.5 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2a00:1450:400c:c09::241 Subject: [Qemu-devel] [PATCH] bt: rewrite csrhci_write to avoid out-of-bounds writes X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" The usage of INT_MAX in this function confuses Coverity. I think the defect is bogus, however there is no protection against getting more than sizeof(s->inpkt) bytes from the character device backend. Rewrite the function to only fill in as much data as needed from buf into s->inpkt. The plen variable is replaced by a simple state machine and there is no need anymore to shift contents to the beginning of s->inpkt. Signed-off-by: Paolo Bonzini --- hw/bt/hci-csr.c | 67 +++++++++++++++++++++++++++++++++++++++------------------ 1 file changed, 46 insertions(+), 21 deletions(-) diff --git a/hw/bt/hci-csr.c b/hw/bt/hci-csr.c index e6b8998..d688372 100644 --- a/hw/bt/hci-csr.c +++ b/hw/bt/hci-csr.c @@ -39,9 +39,14 @@ struct csrhci_s { int out_size; uint8_t outfifo[FIFO_LEN * 2]; uint8_t inpkt[FIFO_LEN]; + enum { + CSR_HDR_LEN, + CSR_DATA_LEN, + CSR_DATA + } in_state; int in_len; int in_hdr; - int in_data; + int in_needed; QEMUTimer *out_tm; int64_t baud_delay; @@ -296,38 +301,60 @@ static int csrhci_data_len(const uint8_t *pkt) exit(-1); } +static void csrhci_ready_for_next_inpkt(struct csrhci_s *s) +{ + s->in_state = CSR_HDR_LEN; + s->in_len = 0; + s->in_needed = 2; + s->in_hdr = INT_MAX; +} + static int csrhci_write(struct CharDriverState *chr, const uint8_t *buf, int len) { struct csrhci_s *s = (struct csrhci_s *) chr->opaque; - int plen = s->in_len; + int total = 0; if (!s->enable) return 0; - s->in_len += len; - memcpy(s->inpkt + plen, buf, len); + for (;;) { + int cnt = MIN(len, s->in_needed - s->in_len); + if (cnt) { + memcpy(s->inpkt + s->in_len, buf, cnt); + s->in_len += cnt; + buf += cnt; + len -= cnt; + total += cnt; + } + + if (s->in_len < s->in_needed) { + break; + } - while (1) { - if (s->in_len >= 2 && plen < 2) + if (s->in_state == CSR_HDR_LEN) { s->in_hdr = csrhci_header_len(s->inpkt) + 1; + assert(s->in_hdr >= s->in_needed); + s->in_needed = s->in_hdr; + s->in_state = CSR_DATA_LEN; + continue; + } - if (s->in_len >= s->in_hdr && plen < s->in_hdr) - s->in_data = csrhci_data_len(s->inpkt) + s->in_hdr; + if (s->in_state == CSR_DATA_LEN) { + s->in_needed += csrhci_data_len(s->inpkt); + /* hci_acl_hdr could specify more than 4096 bytes, so assert. */ + assert(s->in_needed <= sizeof(s->inpkt)); + s->in_state = CSR_DATA; + continue; + } - if (s->in_len >= s->in_data) { + if (s->in_state == CSR_DATA) { csrhci_in_packet(s, s->inpkt); - - memmove(s->inpkt, s->inpkt + s->in_len, s->in_len - s->in_data); - s->in_len -= s->in_data; - s->in_hdr = INT_MAX; - s->in_data = INT_MAX; - plen = 0; - } else - break; + csrhci_ready_for_next_inpkt(s); + } } - return len; + return total; } static void csrhci_out_hci_packet_event(void *opaque, @@ -389,11 +416,9 @@ static void csrhci_reset(struct csrhci_s *s) { s->out_len = 0; s->out_size = FIFO_LEN; - s->in_len = 0; + csrhci_ready_for_next_inpkt(s); s->baud_delay = NANOSECONDS_PER_SECOND; s->enable = 0; - s->in_hdr = INT_MAX; - s->in_data = INT_MAX; s->modem_state = 0; /* After a while... (but sooner than 10ms) */