| Message ID | 20210716155311.5570-1-len.baker@gmx.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] rtw88: Fix out-of-bounds write | expand |
On Fri, Jul 16, 2021 at 05:53:11PM +0200, Len Baker wrote: > In the rtw_pci_init_rx_ring function the "if (len > TRX_BD_IDX_MASK)" > statement guarantees that len is less than or equal to GENMASK(11, 0) or > in other words that len is less than or equal to 4095. However the > rx_ring->buf has a size of RTK_MAX_RX_DESC_NUM (defined as 512). This > way it is possible an out-of-bounds write in the for statement due to > the i variable can exceed the rx_ring->buff size. > > However, this overflow never happens due to the rtw_pci_init_rx_ring is > only ever called with a fixed constant of RTK_MAX_RX_DESC_NUM. But it is > better to be defensive in this case and add a new check to avoid > overflows if this function is called in a future with a value greater > than 512. If this can never happen, then no, this is not needed. Why would you check twice for the same thing? thanks, greg k-h
On Fri, Jul 16, 2021 at 07:20:48PM +0200, Greg KH wrote: > On Fri, Jul 16, 2021 at 05:53:11PM +0200, Len Baker wrote: > > In the rtw_pci_init_rx_ring function the "if (len > TRX_BD_IDX_MASK)" > > statement guarantees that len is less than or equal to GENMASK(11, 0) or > > in other words that len is less than or equal to 4095. However the > > rx_ring->buf has a size of RTK_MAX_RX_DESC_NUM (defined as 512). This > > way it is possible an out-of-bounds write in the for statement due to > > the i variable can exceed the rx_ring->buff size. > > > > However, this overflow never happens due to the rtw_pci_init_rx_ring is > > only ever called with a fixed constant of RTK_MAX_RX_DESC_NUM. But it is > > better to be defensive in this case and add a new check to avoid > > overflows if this function is called in a future with a value greater > > than 512. > > If this can never happen, then no, this is not needed. Then, if this can never happen, the current check would not be necessary either. > Why would you check twice for the same thing? Ok, it makes no sense to double check the "len" variable twice. So, I propose to modify the current check as follows: diff --git a/drivers/net/wireless/realtek/rtw88/pci.c b/drivers/net/wireless/realtek/rtw88/pci.c index e7d17ab8f113..0fd140523868 100644 --- a/drivers/net/wireless/realtek/rtw88/pci.c +++ b/drivers/net/wireless/realtek/rtw88/pci.c @@ -268,8 +268,8 @@ static int rtw_pci_init_rx_ring(struct rtw_dev *rtwdev, int i, allocated; int ret = 0; - if (len > TRX_BD_IDX_MASK) { - rtw_err(rtwdev, "len %d exceeds maximum RX entries\n", len); + if (len > ARRAY_SIZE(rx_ring->buf)) { + rtw_err(rtwdev, "len %d exceeds maximum RX ring buffer\n", len); return -EINVAL; } This way the overflow can never happen with the current call to rtw_pci_init_rx_ring function or with a future call with a "len" parameter greater than 512. What do you think? If there are no objections I will send a v3 for review. Another question: If this can never happen should I include the "Fixes" tag, "Addresses-Coverity-ID" tag and Cc to stable? Thanks, Len > > thanks, > > greg k-h
On Sat, Jul 17, 2021 at 03:33:43PM +0200, Len Baker wrote: > On Fri, Jul 16, 2021 at 07:20:48PM +0200, Greg KH wrote: > > On Fri, Jul 16, 2021 at 05:53:11PM +0200, Len Baker wrote: > > > In the rtw_pci_init_rx_ring function the "if (len > TRX_BD_IDX_MASK)" > > > statement guarantees that len is less than or equal to GENMASK(11, 0) or > > > in other words that len is less than or equal to 4095. However the > > > rx_ring->buf has a size of RTK_MAX_RX_DESC_NUM (defined as 512). This > > > way it is possible an out-of-bounds write in the for statement due to > > > the i variable can exceed the rx_ring->buff size. > > > > > > However, this overflow never happens due to the rtw_pci_init_rx_ring is > > > only ever called with a fixed constant of RTK_MAX_RX_DESC_NUM. But it is > > > better to be defensive in this case and add a new check to avoid > > > overflows if this function is called in a future with a value greater > > > than 512. > > > > If this can never happen, then no, this is not needed. > > Then, if this can never happen, the current check would not be necessary > either. > > > Why would you check twice for the same thing? > > Ok, it makes no sense to double check the "len" variable twice. So, I > propose to modify the current check as follows: > > diff --git a/drivers/net/wireless/realtek/rtw88/pci.c b/drivers/net/wireless/realtek/rtw88/pci.c > index e7d17ab8f113..0fd140523868 100644 > --- a/drivers/net/wireless/realtek/rtw88/pci.c > +++ b/drivers/net/wireless/realtek/rtw88/pci.c > @@ -268,8 +268,8 @@ static int rtw_pci_init_rx_ring(struct rtw_dev *rtwdev, > int i, allocated; > int ret = 0; > > - if (len > TRX_BD_IDX_MASK) { > - rtw_err(rtwdev, "len %d exceeds maximum RX entries\n", len); > + if (len > ARRAY_SIZE(rx_ring->buf)) { > + rtw_err(rtwdev, "len %d exceeds maximum RX ring buffer\n", len); > return -EINVAL; > } > > This way the overflow can never happen with the current call to > rtw_pci_init_rx_ring function or with a future call with a "len" parameter > greater than 512. What do you think? > > If there are no objections I will send a v3 for review. > > Another question: If this can never happen should I include the "Fixes" tag, > "Addresses-Coverity-ID" tag and Cc to stable? If it can never happen, why have this check at all? Looks like a Coverity false positive? thanks, greg k-h
On Sat, Jul 17, 2021 at 07:33:49PM +0200, Greg KH wrote: > On Sat, Jul 17, 2021 at 03:33:43PM +0200, Len Baker wrote: > > Another question: If this can never happen should I include the "Fixes" tag, > > "Addresses-Coverity-ID" tag and Cc to stable? > > If it can never happen, why have this check at all? > > Looks like a Coverity false positive? Ok, then I will remove the check and I will send a patch for review. > > thanks, > > greg k-h Regards, Len
diff --git a/drivers/net/wireless/realtek/rtw88/pci.c b/drivers/net/wireless/realtek/rtw88/pci.c index e7d17ab8f113..53dc90276693 100644 --- a/drivers/net/wireless/realtek/rtw88/pci.c +++ b/drivers/net/wireless/realtek/rtw88/pci.c @@ -273,6 +273,11 @@ static int rtw_pci_init_rx_ring(struct rtw_dev *rtwdev, return -EINVAL; } + if (len > ARRAY_SIZE(rx_ring->buf)) { + rtw_err(rtwdev, "len %d exceeds maximum RX ring buffer\n", len); + return -EINVAL; + } + head = dma_alloc_coherent(&pdev->dev, ring_sz, &dma, GFP_KERNEL); if (!head) { rtw_err(rtwdev, "failed to allocate rx ring\n");
In the rtw_pci_init_rx_ring function the "if (len > TRX_BD_IDX_MASK)" statement guarantees that len is less than or equal to GENMASK(11, 0) or in other words that len is less than or equal to 4095. However the rx_ring->buf has a size of RTK_MAX_RX_DESC_NUM (defined as 512). This way it is possible an out-of-bounds write in the for statement due to the i variable can exceed the rx_ring->buff size. However, this overflow never happens due to the rtw_pci_init_rx_ring is only ever called with a fixed constant of RTK_MAX_RX_DESC_NUM. But it is better to be defensive in this case and add a new check to avoid overflows if this function is called in a future with a value greater than 512. Cc: stable@vger.kernel.org Addresses-Coverity-ID: 1461515 ("Out-of-bounds write") Fixes: e3037485c68ec ("rtw88: new Realtek 802.11ac driver") Signed-off-by: Len Baker <len.baker@gmx.com> --- Changelog v1 -> v2 - Remove the macro ARRAY_SIZE from the for loop (Pkshih, Brian Norris). - Add a new check for the len variable (Pkshih, Brian Norris). drivers/net/wireless/realtek/rtw88/pci.c | 5 +++++ 1 file changed, 5 insertions(+) -- 2.25.1