On 24/03/2021 14.07, Arnd Bergmann wrote: > From: Arnd Bergmann <a...@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 <li...@rasmusvillemoes.dk> > Signed-off-by: Arnd Bergmann <a...@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 <li...@rasmusvillemoes.dk>