linux-kernel - Re: [PATCH -next v2 1/2] fs/ntfs3: Don't use uni1 uninitialized in ntfs_d

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Message-ID: <Y1LSn+O44lCRR3qE@dev-arch.thelio-3990X>
Date:   Fri, 21 Oct 2022 10:10:55 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, ntfs3@...ts.linux.dev,
        llvm@...ts.linux.dev, patches@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next v2 1/2] fs/ntfs3: Don't use uni1 uninitialized in
 ntfs_d_compare()

Ping? This is still breaking our builds in -next...

On Tue, Oct 04, 2022 at 04:23:58PM -0700, Nathan Chancellor wrote:
> Clang warns:
> 
>   fs/ntfs3/namei.c:445:7: error: variable 'uni1' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
>                   if (toupper(c1) != toupper(c2)) {
>                       ^~~~~~~~~~~~~~~~~~~~~~~~~~
>   ./include/linux/ctype.h:64:20: note: expanded from macro 'toupper'
>   #define toupper(c) __toupper(c)
>                     ^
>   fs/ntfs3/namei.c:487:12: note: uninitialized use occurs here
>           __putname(uni1);
>                     ^~~~
>   ./include/linux/fs.h:2789:65: note: expanded from macro '__putname'
>   #define __putname(name)         kmem_cache_free(names_cachep, (void *)(name))
>                                                                         ^~~~
>   fs/ntfs3/namei.c:445:3: note: remove the 'if' if its condition is always false
>                   if (toupper(c1) != toupper(c2)) {
>                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   fs/ntfs3/namei.c:434:7: error: variable 'uni1' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
>                   if (!lm--) {
>                       ^~~~~
>   fs/ntfs3/namei.c:487:12: note: uninitialized use occurs here
>           __putname(uni1);
>                     ^~~~
>   ./include/linux/fs.h:2789:65: note: expanded from macro '__putname'
>   #define __putname(name)         kmem_cache_free(names_cachep, (void *)(name))
>                                                                         ^~~~
>   fs/ntfs3/namei.c:434:3: note: remove the 'if' if its condition is always false
>                   if (!lm--) {
>                   ^~~~~~~~~~~~
>   fs/ntfs3/namei.c:430:22: note: initialize the variable 'uni1' to silence this warning
>           struct cpu_str *uni1, *uni2;
>                               ^
>                               = NULL
>   2 errors generated.
> 
> There is no point in calling __putname() in these particular error
> paths, as there has been no corresponding __getname() call yet. Just
> return directly in these blocks to clear up the warning.
> 
> Fixes: a3a956c78efa ("fs/ntfs3: Add option "nocase"")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1729
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
> 
> v2:
>     * Pick up Nick's reviewed-by tag.
> v1: https://lore.kernel.org/20221004144145.1345772-1-nathan@kernel.org/
> 
>  fs/ntfs3/namei.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/ntfs3/namei.c b/fs/ntfs3/namei.c
> index 315763eb05ff..5d3a6ce3f05f 100644
> --- a/fs/ntfs3/namei.c
> +++ b/fs/ntfs3/namei.c
> @@ -431,10 +431,8 @@ static int ntfs_d_compare(const struct dentry *dentry, unsigned int len1,
>  
>  	/* First try fast implementation. */
>  	for (;;) {
> -		if (!lm--) {
> -			ret = len1 == len2 ? 0 : 1;
> -			goto out;
> -		}
> +		if (!lm--)
> +			return len1 == len2 ? 0 : 1;
>  
>  		if ((c1 = *n1++) == (c2 = *n2++))
>  			continue;
> @@ -442,10 +440,8 @@ static int ntfs_d_compare(const struct dentry *dentry, unsigned int len1,
>  		if (c1 >= 0x80 || c2 >= 0x80)
>  			break;
>  
> -		if (toupper(c1) != toupper(c2)) {
> -			ret = 1;
> -			goto out;
> -		}
> +		if (toupper(c1) != toupper(c2))
> +			return 1;
>  	}
>  
>  	/*
> 
> base-commit: d45da67caedacd500879de5e649360cc70777af7
> -- 
> 2.37.3
> 
>