| Message ID | 20210324130731.1513798-1-arnd@kernel.org |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] hinic: avoid gcc -Wrestrict warning | expand |
On 24/03/2021 14.07, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > With extra warnings enabled, gcc complains that snprintf should not > take the same buffer as source and destination: > > drivers/net/ethernet/huawei/hinic/hinic_ethtool.c: In function 'hinic_set_settings_to_hw': > drivers/net/ethernet/huawei/hinic/hinic_ethtool.c:480:9: error: 'snprintf' argument 4 overlaps destination object 'set_link_str' [-Werror=restrict] > 480 | err = snprintf(set_link_str, SET_LINK_STR_MAX_LEN, > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > 481 | "%sspeed %d ", set_link_str, speed); > | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > drivers/net/ethernet/huawei/hinic/hinic_ethtool.c:464:7: note: destination object referenced by 'restrict'-qualified argument 1 was declared here > 464 | char set_link_str[SET_LINK_STR_MAX_LEN] = {0}; > > Rewrite this to avoid the nested sprintf and instead use separate > buffers, which is simpler. > This looks much better. Thanks. > Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > v2: rework according to feedback from Rasmus. This one could > easily avoid most of the pitfalls > --- > .../net/ethernet/huawei/hinic/hinic_ethtool.c | 25 ++++++++----------- > 1 file changed, 10 insertions(+), 15 deletions(-) > > diff --git a/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c b/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c > index c340d9acba80..d7e20dab6e48 100644 > --- a/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c > +++ b/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c > @@ -34,7 +34,7 @@ > #include "hinic_rx.h" > #include "hinic_dev.h" > > -#define SET_LINK_STR_MAX_LEN 128 > +#define SET_LINK_STR_MAX_LEN 16 > > #define GET_SUPPORTED_MODE 0 > #define GET_ADVERTISED_MODE 1 > @@ -462,24 +462,19 @@ static int hinic_set_settings_to_hw(struct hinic_dev *nic_dev, > { > struct hinic_link_ksettings_info settings = {0}; > char set_link_str[SET_LINK_STR_MAX_LEN] = {0}; > + const char *autoneg_str; > struct net_device *netdev = nic_dev->netdev; > enum nic_speed_level speed_level = 0; > int err; > > - err = snprintf(set_link_str, SET_LINK_STR_MAX_LEN, "%s", > - (set_settings & HILINK_LINK_SET_AUTONEG) ? > - (autoneg ? "autong enable " : "autong disable ") : ""); > - if (err < 0 || err >= SET_LINK_STR_MAX_LEN) { > - netif_err(nic_dev, drv, netdev, "Failed to snprintf link state, function return(%d) and dest_len(%d)\n", > - err, SET_LINK_STR_MAX_LEN); > - return -EFAULT; > - } > + autoneg_str = (set_settings & HILINK_LINK_SET_AUTONEG) ? > + (autoneg ? "autong enable " : "autong disable ") : ""; > > if (set_settings & HILINK_LINK_SET_SPEED) { > speed_level = hinic_ethtool_to_hw_speed_level(speed); > err = snprintf(set_link_str, SET_LINK_STR_MAX_LEN, > - "%sspeed %d ", set_link_str, speed); > - if (err <= 0 || err >= SET_LINK_STR_MAX_LEN) { > + "speed %d ", speed); > + if (err >= SET_LINK_STR_MAX_LEN) { > netif_err(nic_dev, drv, netdev, "Failed to snprintf link speed, function return(%d) and dest_len(%d)\n", > err, SET_LINK_STR_MAX_LEN); > return -EFAULT; It's not your invention of course, but this both seems needlessly harsh and EFAULT is a weird error to return. It's just a printk() message that might be truncated, and now that the format string only has a %d specifier, it can actually be verified statically that overflow will never happen (though I don't know or think gcc can do that, perhaps there's some locale nonsense in the standard that allows using utf16-encoded sanskrit runes). So probably that test should just be dropped, but that's a separate thing. Reviewed-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
On Wed, Mar 24, 2021 at 2:29 PM Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote: > On 24/03/2021 14.07, Arnd Bergmann wrote: > > > if (set_settings & HILINK_LINK_SET_SPEED) { > > speed_level = hinic_ethtool_to_hw_speed_level(speed); > > err = snprintf(set_link_str, SET_LINK_STR_MAX_LEN, > > - "%sspeed %d ", set_link_str, speed); > > - if (err <= 0 || err >= SET_LINK_STR_MAX_LEN) { > > + "speed %d ", speed); > > + if (err >= SET_LINK_STR_MAX_LEN) { > > netif_err(nic_dev, drv, netdev, "Failed to snprintf link speed, function return(%d) and dest_len(%d)\n", > > err, SET_LINK_STR_MAX_LEN); > > return -EFAULT; > > It's not your invention of course, but this both seems needlessly harsh > and EFAULT is a weird error to return. It's just a printk() message that > might be truncated, and now that the format string only has a %d > specifier, it can actually be verified statically that overflow will > never happen (though I don't know or think gcc can do that, perhaps > there's some locale nonsense in the standard that allows using > utf16-encoded sanskrit runes). So probably that test should just be > dropped, but that's a separate thing. I thought about fixing it, but this seemed to be a rabbit hole I didn't want to get into, as there are other harmless issues in the driver that could be improved. I'm fairly sure gcc can indeed warn about the overflow with -Wformat-truncation, but the warning is disabled at the moment because it has a ton of false positives: kernel/workqueue.c: In function 'create_worker': kernel/workqueue.c:1933:55: error: '%d' directive output may be truncated writing between 1 and 10 bytes into a region of size between 3 and 13 [-Werror=format-truncation=] 1933 | snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id); Arnd
Hello: This patch was applied to netdev/net-next.git (refs/heads/master): On Wed, 24 Mar 2021 14:07:22 +0100 you wrote: > From: Arnd Bergmann <arnd@arndb.de> > > With extra warnings enabled, gcc complains that snprintf should not > take the same buffer as source and destination: > > drivers/net/ethernet/huawei/hinic/hinic_ethtool.c: In function 'hinic_set_settings_to_hw': > drivers/net/ethernet/huawei/hinic/hinic_ethtool.c:480:9: error: 'snprintf' argument 4 overlaps destination object 'set_link_str' [-Werror=restrict] > 480 | err = snprintf(set_link_str, SET_LINK_STR_MAX_LEN, > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > 481 | "%sspeed %d ", set_link_str, speed); > | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > drivers/net/ethernet/huawei/hinic/hinic_ethtool.c:464:7: note: destination object referenced by 'restrict'-qualified argument 1 was declared here > 464 | char set_link_str[SET_LINK_STR_MAX_LEN] = {0}; > > [...] Here is the summary with links: - [v2] hinic: avoid gcc -Wrestrict warning https://git.kernel.org/netdev/net-next/c/84c7f6c33f42 You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
diff --git a/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c b/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c index c340d9acba80..d7e20dab6e48 100644 --- a/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c +++ b/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c @@ -34,7 +34,7 @@ #include "hinic_rx.h" #include "hinic_dev.h" -#define SET_LINK_STR_MAX_LEN 128 +#define SET_LINK_STR_MAX_LEN 16 #define GET_SUPPORTED_MODE 0 #define GET_ADVERTISED_MODE 1 @@ -462,24 +462,19 @@ static int hinic_set_settings_to_hw(struct hinic_dev *nic_dev, { struct hinic_link_ksettings_info settings = {0}; char set_link_str[SET_LINK_STR_MAX_LEN] = {0}; + const char *autoneg_str; struct net_device *netdev = nic_dev->netdev; enum nic_speed_level speed_level = 0; int err; - err = snprintf(set_link_str, SET_LINK_STR_MAX_LEN, "%s", - (set_settings & HILINK_LINK_SET_AUTONEG) ? - (autoneg ? "autong enable " : "autong disable ") : ""); - if (err < 0 || err >= SET_LINK_STR_MAX_LEN) { - netif_err(nic_dev, drv, netdev, "Failed to snprintf link state, function return(%d) and dest_len(%d)\n", - err, SET_LINK_STR_MAX_LEN); - return -EFAULT; - } + autoneg_str = (set_settings & HILINK_LINK_SET_AUTONEG) ? + (autoneg ? "autong enable " : "autong disable ") : ""; if (set_settings & HILINK_LINK_SET_SPEED) { speed_level = hinic_ethtool_to_hw_speed_level(speed); err = snprintf(set_link_str, SET_LINK_STR_MAX_LEN, - "%sspeed %d ", set_link_str, speed); - if (err <= 0 || err >= SET_LINK_STR_MAX_LEN) { + "speed %d ", speed); + if (err >= SET_LINK_STR_MAX_LEN) { netif_err(nic_dev, drv, netdev, "Failed to snprintf link speed, function return(%d) and dest_len(%d)\n", err, SET_LINK_STR_MAX_LEN); return -EFAULT; @@ -494,11 +489,11 @@ static int hinic_set_settings_to_hw(struct hinic_dev *nic_dev, err = hinic_set_link_settings(nic_dev->hwdev, &settings); if (err != HINIC_MGMT_CMD_UNSUPPORTED) { if (err) - netif_err(nic_dev, drv, netdev, "Set %s failed\n", - set_link_str); + netif_err(nic_dev, drv, netdev, "Set %s%sfailed\n", + autoneg_str, set_link_str); else - netif_info(nic_dev, drv, netdev, "Set %s successfully\n", - set_link_str); + netif_info(nic_dev, drv, netdev, "Set %s%ssuccessfully\n", + autoneg_str, set_link_str); return err; }