* [PATCH] staging: rtl8192u: Remove an unnecessary NULL check @ 2019-05-21 17:42 Nathan Chancellor 2019-05-21 22:53 ` Nick Desaulniers 2019-05-22 7:04 ` Dan Carpenter 0 siblings, 2 replies; 6+ messages in thread From: Nathan Chancellor @ 2019-05-21 17:42 UTC (permalink / raw) To: Greg Kroah-Hartman Cc: John Whitmore, devel, linux-kernel, clang-built-linux, Nick Desaulniers, Nathan Chancellor Clang warns: drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c:2663:47: warning: address of array 'param->u.wpa_ie.data' will always evaluate to 'true' [-Wpointer-bool-conversion] (param->u.wpa_ie.len && !param->u.wpa_ie.data)) ~~~~~~~~~~~~~~~~~^~~~ This was exposed by commit deabe03523a7 ("Staging: rtl8192u: ieee80211: Use !x in place of NULL comparisons") because we disable the warning that would have pointed out the comparison against NULL is also false: drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c:2663:46: warning: comparison of array 'param->u.wpa_ie.data' equal to a null pointer is always false [-Wtautological-pointer-compare] (param->u.wpa_ie.len && param->u.wpa_ie.data == NULL)) ~~~~~~~~~~~~~~~~^~~~ ~~~~ Remove it so clang no longer warns. Link: https://github.com/ClangBuiltLinux/linux/issues/487 Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> --- drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c b/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c index f38f9d8b78bb..e0da0900a4f7 100644 --- a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c +++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c @@ -2659,8 +2659,7 @@ static int ieee80211_wpa_set_wpa_ie(struct ieee80211_device *ieee, { u8 *buf; - if (param->u.wpa_ie.len > MAX_WPA_IE_LEN || - (param->u.wpa_ie.len && !param->u.wpa_ie.data)) + if (param->u.wpa_ie.len > MAX_WPA_IE_LEN) return -EINVAL; if (param->u.wpa_ie.len) { -- 2.22.0.rc1 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] staging: rtl8192u: Remove an unnecessary NULL check 2019-05-21 17:42 [PATCH] staging: rtl8192u: Remove an unnecessary NULL check Nathan Chancellor @ 2019-05-21 22:53 ` Nick Desaulniers 2019-05-21 22:57 ` Nick Desaulniers 2019-05-22 7:04 ` Dan Carpenter 1 sibling, 1 reply; 6+ messages in thread From: Nick Desaulniers @ 2019-05-21 22:53 UTC (permalink / raw) To: Nathan Chancellor Cc: Greg Kroah-Hartman, John Whitmore, devel, LKML, clang-built-linux, rsmith On Tue, May 21, 2019 at 10:42 AM Nathan Chancellor <natechancellor@gmail.com> wrote: > > Clang warns: > > drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c:2663:47: warning: > address of array 'param->u.wpa_ie.data' will always evaluate to 'true' > [-Wpointer-bool-conversion] > (param->u.wpa_ie.len && !param->u.wpa_ie.data)) > ~~~~~~~~~~~~~~~~~^~~~ > > This was exposed by commit deabe03523a7 ("Staging: rtl8192u: ieee80211: > Use !x in place of NULL comparisons") because we disable the warning > that would have pointed out the comparison against NULL is also false: > > drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c:2663:46: warning: > comparison of array 'param->u.wpa_ie.data' equal to a null pointer is > always false [-Wtautological-pointer-compare] > (param->u.wpa_ie.len && param->u.wpa_ie.data == NULL)) > ~~~~~~~~~~~~~~~~^~~~ ~~~~ > > Remove it so clang no longer warns. > > Link: https://github.com/ClangBuiltLinux/linux/issues/487 > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> > --- > drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c b/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c > index f38f9d8b78bb..e0da0900a4f7 100644 > --- a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c > +++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c > @@ -2659,8 +2659,7 @@ static int ieee80211_wpa_set_wpa_ie(struct ieee80211_device *ieee, > { > u8 *buf; > > - if (param->u.wpa_ie.len > MAX_WPA_IE_LEN || > - (param->u.wpa_ie.len && !param->u.wpa_ie.data)) Right so, the types in this expression: param: struct ieee_param* param->u: *anonymous union* param->u.wpa_ie: *anonymous struct* param->u.wpa_ie.len: u32 param->u.wpa_ie.data: u8 [0] as defined in drivers/staging/rtl8192u/ieee80211/ieee80211.h#L295 https://github.com/ClangBuiltLinux/linux/blob/9c7db5004280767566e91a33445bf93aa479ef02/drivers/staging/rtl8192u/ieee80211/ieee80211.h#L295-L322 so this is a tricky case, because in general array members can never themselves be NULL, and usually I trust -Wpointer-bool-conversion, but this is a special case because of the flexible array member: https://en.wikipedia.org/wiki/Flexible_array_member. (It seems that having the 0 in the length explicitly was pre-c99 GNU extension: https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html). I wonder if -Wtautological-pointer-compare applies to Flexible Array Members or not (Richard, do you know)? In general, you'd be setting param->u.wpa_ie to the return value of a dynamic memory allocation, not param->u.wpa_ie.data, so this check is fishy to me. > + if (param->u.wpa_ie.len > MAX_WPA_IE_LEN) > return -EINVAL; > > if (param->u.wpa_ie.len) { > -- > 2.22.0.rc1 > -- Thanks, ~Nick Desaulniers ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] staging: rtl8192u: Remove an unnecessary NULL check 2019-05-21 22:53 ` Nick Desaulniers @ 2019-05-21 22:57 ` Nick Desaulniers 2019-05-22 9:24 ` Dan Carpenter 0 siblings, 1 reply; 6+ messages in thread From: Nick Desaulniers @ 2019-05-21 22:57 UTC (permalink / raw) To: Nathan Chancellor Cc: Greg Kroah-Hartman, John Whitmore, devel, LKML, clang-built-linux, Richard Smith + Richard for real this time. On Tue, May 21, 2019 at 3:53 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Tue, May 21, 2019 at 10:42 AM Nathan Chancellor > <natechancellor@gmail.com> wrote: > > > > Clang warns: > > > > drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c:2663:47: warning: > > address of array 'param->u.wpa_ie.data' will always evaluate to 'true' > > [-Wpointer-bool-conversion] > > (param->u.wpa_ie.len && !param->u.wpa_ie.data)) > > ~~~~~~~~~~~~~~~~~^~~~ > > > > This was exposed by commit deabe03523a7 ("Staging: rtl8192u: ieee80211: > > Use !x in place of NULL comparisons") because we disable the warning > > that would have pointed out the comparison against NULL is also false: > > > > drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c:2663:46: warning: > > comparison of array 'param->u.wpa_ie.data' equal to a null pointer is > > always false [-Wtautological-pointer-compare] > > (param->u.wpa_ie.len && param->u.wpa_ie.data == NULL)) > > ~~~~~~~~~~~~~~~~^~~~ ~~~~ > > > > Remove it so clang no longer warns. > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/487 > > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> > > --- > > drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c b/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c > > index f38f9d8b78bb..e0da0900a4f7 100644 > > --- a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c > > +++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c > > @@ -2659,8 +2659,7 @@ static int ieee80211_wpa_set_wpa_ie(struct ieee80211_device *ieee, > > { > > u8 *buf; > > > > - if (param->u.wpa_ie.len > MAX_WPA_IE_LEN || > > - (param->u.wpa_ie.len && !param->u.wpa_ie.data)) > > Right so, the types in this expression: > > param: struct ieee_param* > param->u: *anonymous union* > param->u.wpa_ie: *anonymous struct* > param->u.wpa_ie.len: u32 > param->u.wpa_ie.data: u8 [0] > as defined in drivers/staging/rtl8192u/ieee80211/ieee80211.h#L295 > https://github.com/ClangBuiltLinux/linux/blob/9c7db5004280767566e91a33445bf93aa479ef02/drivers/staging/rtl8192u/ieee80211/ieee80211.h#L295-L322 > > so this is a tricky case, because in general array members can never > themselves be NULL, and usually I trust -Wpointer-bool-conversion, but > this is a special case because of the flexible array member: > https://en.wikipedia.org/wiki/Flexible_array_member. (It seems that > having the 0 in the length explicitly was pre-c99 GNU extension: > https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html). I wonder if > -Wtautological-pointer-compare applies to Flexible Array Members or > not (Richard, do you know)? In general, you'd be setting > param->u.wpa_ie to the return value of a dynamic memory allocation, > not param->u.wpa_ie.data, so this check is fishy to me. > > > + if (param->u.wpa_ie.len > MAX_WPA_IE_LEN) > > return -EINVAL; > > > > if (param->u.wpa_ie.len) { > > -- > > 2.22.0.rc1 > > > > > -- > Thanks, > ~Nick Desaulniers -- Thanks, ~Nick Desaulniers ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] staging: rtl8192u: Remove an unnecessary NULL check 2019-05-21 22:57 ` Nick Desaulniers @ 2019-05-22 9:24 ` Dan Carpenter 0 siblings, 0 replies; 6+ messages in thread From: Dan Carpenter @ 2019-05-22 9:24 UTC (permalink / raw) To: Nick Desaulniers Cc: Nathan Chancellor, devel, Greg Kroah-Hartman, LKML, John Whitmore, clang-built-linux, Richard Smith On Tue, May 21, 2019 at 03:57:46PM -0700, Nick Desaulniers wrote: > > > - if (param->u.wpa_ie.len > MAX_WPA_IE_LEN || > > > - (param->u.wpa_ie.len && !param->u.wpa_ie.data)) > > > > Right so, the types in this expression: > > > > param: struct ieee_param* > > param->u: *anonymous union* > > param->u.wpa_ie: *anonymous struct* > > param->u.wpa_ie.len: u32 > > param->u.wpa_ie.data: u8 [0] > > as defined in drivers/staging/rtl8192u/ieee80211/ieee80211.h#L295 > > https://github.com/ClangBuiltLinux/linux/blob/9c7db5004280767566e91a33445bf93aa479ef02/drivers/staging/rtl8192u/ieee80211/ieee80211.h#L295-L322 > > > > so this is a tricky case, because in general array members can never > > themselves be NULL, Unless they array was the first struct member, obviously. > > and usually I trust -Wpointer-bool-conversion, but > > this is a special case because of the flexible array member: Nah. It's the same thing. That patch is fine. regards, dan carpenter ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] staging: rtl8192u: Remove an unnecessary NULL check 2019-05-21 17:42 [PATCH] staging: rtl8192u: Remove an unnecessary NULL check Nathan Chancellor 2019-05-21 22:53 ` Nick Desaulniers @ 2019-05-22 7:04 ` Dan Carpenter 2019-05-22 20:39 ` Nathan Chancellor 1 sibling, 1 reply; 6+ messages in thread From: Dan Carpenter @ 2019-05-22 7:04 UTC (permalink / raw) To: Nathan Chancellor Cc: Greg Kroah-Hartman, devel, Nick Desaulniers, linux-kernel, John Whitmore, clang-built-linux On Tue, May 21, 2019 at 10:42:21AM -0700, Nathan Chancellor wrote: > Clang warns: > > drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c:2663:47: warning: > address of array 'param->u.wpa_ie.data' will always evaluate to 'true' > [-Wpointer-bool-conversion] > (param->u.wpa_ie.len && !param->u.wpa_ie.data)) > ~~~~~~~~~~~~~~~~~^~~~ > > This was exposed by commit deabe03523a7 ("Staging: rtl8192u: ieee80211: > Use !x in place of NULL comparisons") because we disable the warning > that would have pointed out the comparison against NULL is also false: > Heh. Weird. Why would people disable one and not the other? regards, dan carpenter ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] staging: rtl8192u: Remove an unnecessary NULL check 2019-05-22 7:04 ` Dan Carpenter @ 2019-05-22 20:39 ` Nathan Chancellor 0 siblings, 0 replies; 6+ messages in thread From: Nathan Chancellor @ 2019-05-22 20:39 UTC (permalink / raw) To: Dan Carpenter Cc: Greg Kroah-Hartman, devel, Nick Desaulniers, linux-kernel, John Whitmore, clang-built-linux On Wed, May 22, 2019 at 10:04:18AM +0300, Dan Carpenter wrote: > On Tue, May 21, 2019 at 10:42:21AM -0700, Nathan Chancellor wrote: > > Clang warns: > > > > drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c:2663:47: warning: > > address of array 'param->u.wpa_ie.data' will always evaluate to 'true' > > [-Wpointer-bool-conversion] > > (param->u.wpa_ie.len && !param->u.wpa_ie.data)) > > ~~~~~~~~~~~~~~~~~^~~~ > > > > This was exposed by commit deabe03523a7 ("Staging: rtl8192u: ieee80211: > > Use !x in place of NULL comparisons") because we disable the warning > > that would have pointed out the comparison against NULL is also false: > > > > Heh. Weird. Why would people disable one and not the other? > > regards, > dan carpenter > -Wtautological-compare has a lot of different sub-warnings under it, one of which is the one shown. -Wno-tautological-compare turns off all of those other sub-warnings. The reason that was done is there are quite a few of them: https://gist.github.com/nathanchance/3336adc6e796b57eadd53b106b96c569 https://clang.llvm.org/docs/DiagnosticsReference.html#wtautological-compare It is probably worth looking into turning that on, I'm going to try to do that as I have time. Cheers, Nathan ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2019-05-22 20:39 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2019-05-21 17:42 [PATCH] staging: rtl8192u: Remove an unnecessary NULL check Nathan Chancellor 2019-05-21 22:53 ` Nick Desaulniers 2019-05-21 22:57 ` Nick Desaulniers 2019-05-22 9:24 ` Dan Carpenter 2019-05-22 7:04 ` Dan Carpenter 2019-05-22 20:39 ` Nathan Chancellor
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