| Message ID | 20180625124538.21051-3-shorne@gmail.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Herbert Xu |
| Headers | show |
Le 25/06/2018 à 14:45, Stafford Horne a écrit : > When compiling with GCC 9.0.0 I am seeing the following warning: > > In function ‘fill_kobj_path’, > inlined from ‘kobject_get_path’ at lib/kobject.c:155:2: > lib/kobject.c:128:3: warning: ‘strncpy’ output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation] > strncpy(path + length, kobject_name(parent), cur); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > lib/kobject.c: In function ‘kobject_get_path’: > lib/kobject.c:125:13: note: length computed here > int cur = strlen(kobject_name(parent)); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > This is not really an issue since the buffer we are writing to is > pre-zero'd and we have already allocated the buffer based on the > calculated strlen size and accounted for the terminating '\0'. > Just use memcpy() instead. If we are already sure the destination is big enough, why not just do a strcpy() and drop the 'cur = strlen()' ? Christophe > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Eric Biggers <ebiggers3@gmail.com> > Signed-off-by: Stafford Horne <shorne@gmail.com> > --- > lib/kobject.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/lib/kobject.c b/lib/kobject.c > index 18989b5b3b56..e876957743c8 100644 > --- a/lib/kobject.c > +++ b/lib/kobject.c > @@ -125,7 +125,7 @@ static void fill_kobj_path(struct kobject *kobj, char *path, int length) > int cur = strlen(kobject_name(parent)); > /* back up enough to print this name with '/' */ > length -= cur; > - strncpy(path + length, kobject_name(parent), cur); > + memcpy(path + length, kobject_name(parent), cur); > *(path + --length) = '/'; > } > >
On Mon, Jun 25, 2018 at 02:57:13PM +0200, Christophe LEROY wrote: > > > Le 25/06/2018 à 14:45, Stafford Horne a écrit : > > When compiling with GCC 9.0.0 I am seeing the following warning: > > > > In function ‘fill_kobj_path’, > > inlined from ‘kobject_get_path’ at lib/kobject.c:155:2: > > lib/kobject.c:128:3: warning: ‘strncpy’ output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation] > > strncpy(path + length, kobject_name(parent), cur); > > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > lib/kobject.c: In function ‘kobject_get_path’: > > lib/kobject.c:125:13: note: length computed here > > int cur = strlen(kobject_name(parent)); > > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > > This is not really an issue since the buffer we are writing to is > > pre-zero'd and we have already allocated the buffer based on the > > calculated strlen size and accounted for the terminating '\0'. > > Just use memcpy() instead. > > If we are already sure the destination is big enough, why not just do a > strcpy() and drop the 'cur = strlen()' ? Hi Christophe, Here were are writing multiple strings into a buffer from back to front. We are copying exactly strlen() bytes at a time to avoid the nul terminator being copied into the buffer. I don't doubt we could use strcpy() but I was trying to keep the change small. -Stafford > > > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > Cc: Arnd Bergmann <arnd@arndb.de> > > Cc: Eric Biggers <ebiggers3@gmail.com> > > Signed-off-by: Stafford Horne <shorne@gmail.com> > > --- > > lib/kobject.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/lib/kobject.c b/lib/kobject.c > > index 18989b5b3b56..e876957743c8 100644 > > --- a/lib/kobject.c > > +++ b/lib/kobject.c > > @@ -125,7 +125,7 @@ static void fill_kobj_path(struct kobject *kobj, char *path, int length) > > int cur = strlen(kobject_name(parent)); > > /* back up enough to print this name with '/' */ > > length -= cur; > > - strncpy(path + length, kobject_name(parent), cur); > > + memcpy(path + length, kobject_name(parent), cur); > > *(path + --length) = '/'; > > } > >
Le 25/06/2018 à 15:24, Stafford Horne a écrit : > On Mon, Jun 25, 2018 at 02:57:13PM +0200, Christophe LEROY wrote: >> >> >> Le 25/06/2018 à 14:45, Stafford Horne a écrit : >>> When compiling with GCC 9.0.0 I am seeing the following warning: >>> >>> In function ‘fill_kobj_path’, >>> inlined from ‘kobject_get_path’ at lib/kobject.c:155:2: >>> lib/kobject.c:128:3: warning: ‘strncpy’ output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation] >>> strncpy(path + length, kobject_name(parent), cur); >>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>> lib/kobject.c: In function ‘kobject_get_path’: >>> lib/kobject.c:125:13: note: length computed here >>> int cur = strlen(kobject_name(parent)); >>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>> >>> This is not really an issue since the buffer we are writing to is >>> pre-zero'd and we have already allocated the buffer based on the >>> calculated strlen size and accounted for the terminating '\0'. >>> Just use memcpy() instead. >> >> If we are already sure the destination is big enough, why not just do a >> strcpy() and drop the 'cur = strlen()' ? > > Hi Christophe, > > Here were are writing multiple strings into a buffer from back to front. We are > copying exactly strlen() bytes at a time to avoid the nul terminator being > copied into the buffer. > > I don't doubt we could use strcpy() but I was trying to keep the change small. Ok, fair enough. Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr> > > -Stafford > >>> >>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> >>> Cc: Arnd Bergmann <arnd@arndb.de> >>> Cc: Eric Biggers <ebiggers3@gmail.com> >>> Signed-off-by: Stafford Horne <shorne@gmail.com> >>> --- >>> lib/kobject.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/lib/kobject.c b/lib/kobject.c >>> index 18989b5b3b56..e876957743c8 100644 >>> --- a/lib/kobject.c >>> +++ b/lib/kobject.c >>> @@ -125,7 +125,7 @@ static void fill_kobj_path(struct kobject *kobj, char *path, int length) >>> int cur = strlen(kobject_name(parent)); >>> /* back up enough to print this name with '/' */ >>> length -= cur; >>> - strncpy(path + length, kobject_name(parent), cur); >>> + memcpy(path + length, kobject_name(parent), cur); >>> *(path + --length) = '/'; >>> } >>>
diff --git a/lib/kobject.c b/lib/kobject.c index 18989b5b3b56..e876957743c8 100644 --- a/lib/kobject.c +++ b/lib/kobject.c @@ -125,7 +125,7 @@ static void fill_kobj_path(struct kobject *kobj, char *path, int length) int cur = strlen(kobject_name(parent)); /* back up enough to print this name with '/' */ length -= cur; - strncpy(path + length, kobject_name(parent), cur); + memcpy(path + length, kobject_name(parent), cur); *(path + --length) = '/'; }
When compiling with GCC 9.0.0 I am seeing the following warning: In function ‘fill_kobj_path’, inlined from ‘kobject_get_path’ at lib/kobject.c:155:2: lib/kobject.c:128:3: warning: ‘strncpy’ output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation] strncpy(path + length, kobject_name(parent), cur); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ lib/kobject.c: In function ‘kobject_get_path’: lib/kobject.c:125:13: note: length computed here int cur = strlen(kobject_name(parent)); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ This is not really an issue since the buffer we are writing to is pre-zero'd and we have already allocated the buffer based on the calculated strlen size and accounted for the terminating '\0'. Just use memcpy() instead. Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Eric Biggers <ebiggers3@gmail.com> Signed-off-by: Stafford Horne <shorne@gmail.com> --- lib/kobject.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)