diff mbox series

[v2] scsi: target: Replace strlcpy with strscpy

Message ID 20230830210724.4156575-1-azeemshaikh38@gmail.com (mailing list archive)
State Superseded
Headers show
Series [v2] scsi: target: Replace strlcpy with strscpy | expand

Commit Message

Azeem Shaikh Aug. 30, 2023, 9:07 p.m. UTC 
strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().

Direct replacement is safe here since return value of -errno
is used to check for truncation instead of sizeof(dest).

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
---
v2:
 * Replace all instances of strlcpy in this file instead of just 1.

v1:
 * https://lore.kernel.org/all/20230830200717.4129442-1-azeemshaikh38@gmail.com/

 drivers/target/target_core_configfs.c |   27 ++++++++++++---------------
 1 file changed, 12 insertions(+), 15 deletions(-)

--
2.42.0.283.g2d96d420d3-goog

Comments

Justin Stitt Aug. 30, 2023, 9:53 p.m. UTC | #1 
On Wed, Aug 30, 2023 at 09:07:24PM +0000, Azeem Shaikh wrote:
> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
>
> Direct replacement is safe here since return value of -errno
> is used to check for truncation instead of sizeof(dest).
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
>
> Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
> ---
> v2:
>  * Replace all instances of strlcpy in this file instead of just 1.
>
> v1:
>  * https://lore.kernel.org/all/20230830200717.4129442-1-azeemshaikh38@gmail.com/
>
>  drivers/target/target_core_configfs.c |   27 ++++++++++++---------------
>  1 file changed, 12 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
> index 936e5ff1b209..10a22a428267 100644
> --- a/drivers/target/target_core_configfs.c
> +++ b/drivers/target/target_core_configfs.c
> @@ -1392,16 +1392,15 @@ static ssize_t target_wwn_vendor_id_store(struct config_item *item,
>  	/* +2 to allow for a trailing (stripped) '\n' and null-terminator */
>  	unsigned char buf[INQUIRY_VENDOR_LEN + 2];
>  	char *stripped = NULL;
> -	size_t len;
> +	ssize_t len;
>  	ssize_t ret;
>
> -	len = strlcpy(buf, page, sizeof(buf));
> -	if (len < sizeof(buf)) {
> +	len = strscpy(buf, page, sizeof(buf));
> +	if (len > 0) {
>  		/* Strip any newline added from userspace. */
>  		stripped = strstrip(buf);
> -		len = strlen(stripped);
>  	}
> -	if (len > INQUIRY_VENDOR_LEN) {
> +	if (len < 0 || strlen(stripped) > INQUIRY_VENDOR_LEN) {
>  		pr_err("Emulated T10 Vendor Identification exceeds"
>  			" INQUIRY_VENDOR_LEN: " __stringify(INQUIRY_VENDOR_LEN)
>  			"\n");

Should we be explicitly checking for `len == -E2BIG` instead of the more
generic `len < 0`? Perhaps this is a nitpick but I prefer the former.

...

> @@ -1448,16 +1447,15 @@ static ssize_t target_wwn_product_id_store(struct config_item *item,
>  	/* +2 to allow for a trailing (stripped) '\n' and null-terminator */
>  	unsigned char buf[INQUIRY_MODEL_LEN + 2];
>  	char *stripped = NULL;
> -	size_t len;
> +	ssize_t len;
>  	ssize_t ret;
>
> -	len = strlcpy(buf, page, sizeof(buf));
> -	if (len < sizeof(buf)) {
> +	len = strscpy(buf, page, sizeof(buf));
> +	if (len > 0) {
>  		/* Strip any newline added from userspace. */
>  		stripped = strstrip(buf);
> -		len = strlen(stripped);
>  	}
> -	if (len > INQUIRY_MODEL_LEN) {
> +	if (len < 0 || strlen(stripped) > INQUIRY_MODEL_LEN) {
>  		pr_err("Emulated T10 Vendor exceeds INQUIRY_MODEL_LEN: "
>  			 __stringify(INQUIRY_MODEL_LEN)
>  			"\n");

... and here


> @@ -1504,16 +1502,15 @@ static ssize_t target_wwn_revision_store(struct config_item *item,
>  	/* +2 to allow for a trailing (stripped) '\n' and null-terminator */
>  	unsigned char buf[INQUIRY_REVISION_LEN + 2];
>  	char *stripped = NULL;
> -	size_t len;
> +	ssize_t len;
>  	ssize_t ret;
>
> -	len = strlcpy(buf, page, sizeof(buf));
> -	if (len < sizeof(buf)) {
> +	len = strscpy(buf, page, sizeof(buf));
> +	if (len > 0) {
>  		/* Strip any newline added from userspace. */
>  		stripped = strstrip(buf);
> -		len = strlen(stripped);
>  	}
> -	if (len > INQUIRY_REVISION_LEN) {
> +	if (len < 0 || strlen(stripped) > INQUIRY_REVISION_LEN) {
>  		pr_err("Emulated T10 Revision exceeds INQUIRY_REVISION_LEN: "
>  			 __stringify(INQUIRY_REVISION_LEN)
>  			"\n");

... and here

> --
> 2.42.0.283.g2d96d420d3-goog
>
>

At any rate, this is a worthwhile change for the reasons you mentioned.

Reviewed-by: Justin Stitt <justinstitt@google.com>
Azeem Shaikh Aug. 30, 2023, 10:01 p.m. UTC | #2 
On Wed, Aug 30, 2023 at 5:53 PM Justin Stitt <justinstitt@google.com> wrote:
>
> On Wed, Aug 30, 2023 at 09:07:24PM +0000, Azeem Shaikh wrote:
> > strlcpy() reads the entire source buffer first.
> > This read may exceed the destination size limit.
> > This is both inefficient and can lead to linear read
> > overflows if a source string is not NUL-terminated [1].
> > In an effort to remove strlcpy() completely [2], replace
> > strlcpy() here with strscpy().
> >
> > Direct replacement is safe here since return value of -errno
> > is used to check for truncation instead of sizeof(dest).
> >
> > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> > [2] https://github.com/KSPP/linux/issues/89
> >
> > Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
> > ---
> > v2:
> >  * Replace all instances of strlcpy in this file instead of just 1.
> >
> > v1:
> >  * https://lore.kernel.org/all/20230830200717.4129442-1-azeemshaikh38@gmail.com/
> >
> >  drivers/target/target_core_configfs.c |   27 ++++++++++++---------------
> >  1 file changed, 12 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
> > index 936e5ff1b209..10a22a428267 100644
> > --- a/drivers/target/target_core_configfs.c
> > +++ b/drivers/target/target_core_configfs.c
> > @@ -1392,16 +1392,15 @@ static ssize_t target_wwn_vendor_id_store(struct config_item *item,
> >       /* +2 to allow for a trailing (stripped) '\n' and null-terminator */
> >       unsigned char buf[INQUIRY_VENDOR_LEN + 2];
> >       char *stripped = NULL;
> > -     size_t len;
> > +     ssize_t len;
> >       ssize_t ret;
> >
> > -     len = strlcpy(buf, page, sizeof(buf));
> > -     if (len < sizeof(buf)) {
> > +     len = strscpy(buf, page, sizeof(buf));
> > +     if (len > 0) {
> >               /* Strip any newline added from userspace. */
> >               stripped = strstrip(buf);
> > -             len = strlen(stripped);
> >       }
> > -     if (len > INQUIRY_VENDOR_LEN) {
> > +     if (len < 0 || strlen(stripped) > INQUIRY_VENDOR_LEN) {
> >               pr_err("Emulated T10 Vendor Identification exceeds"
> >                       " INQUIRY_VENDOR_LEN: " __stringify(INQUIRY_VENDOR_LEN)
> >                       "\n");
>
> Should we be explicitly checking for `len == -E2BIG` instead of the more
> generic `len < 0`? Perhaps this is a nitpick but I prefer the former.
>

Most maintainers to whom I have sent such patches in the past have
preferred `len < 0` since it is not "rigid" in checking for -E2BIG
which is an implementation detail of strscpy.
Kees Cook Aug. 30, 2023, 10:38 p.m. UTC | #3 
On Wed, Aug 30, 2023 at 09:07:24PM +0000, Azeem Shaikh wrote:
> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
> 
> Direct replacement is safe here since return value of -errno
> is used to check for truncation instead of sizeof(dest).
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
> 
> Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
> ---
> v2:
>  * Replace all instances of strlcpy in this file instead of just 1.
> 
> v1:
>  * https://lore.kernel.org/all/20230830200717.4129442-1-azeemshaikh38@gmail.com/
> 
>  drivers/target/target_core_configfs.c |   27 ++++++++++++---------------
>  1 file changed, 12 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
> index 936e5ff1b209..10a22a428267 100644
> --- a/drivers/target/target_core_configfs.c
> +++ b/drivers/target/target_core_configfs.c
> @@ -1392,16 +1392,15 @@ static ssize_t target_wwn_vendor_id_store(struct config_item *item,
>  	/* +2 to allow for a trailing (stripped) '\n' and null-terminator */
>  	unsigned char buf[INQUIRY_VENDOR_LEN + 2];
>  	char *stripped = NULL;
> -	size_t len;
> +	ssize_t len;
>  	ssize_t ret;
> 
> -	len = strlcpy(buf, page, sizeof(buf));
> -	if (len < sizeof(buf)) {
> +	len = strscpy(buf, page, sizeof(buf));
> +	if (len > 0) {
>  		/* Strip any newline added from userspace. */
>  		stripped = strstrip(buf);
> -		len = strlen(stripped);
>  	}
> -	if (len > INQUIRY_VENDOR_LEN) {
> +	if (len < 0 || strlen(stripped) > INQUIRY_VENDOR_LEN) {
>  		pr_err("Emulated T10 Vendor Identification exceeds"
>  			" INQUIRY_VENDOR_LEN: " __stringify(INQUIRY_VENDOR_LEN)
>  			"\n");

I would find these more readable if the "len = strlen" were left and the
final "if" becomes:

	if (len < 0 || len > INQUIRY_VENDOR_LEN)

> @@ -1448,16 +1447,15 @@ static ssize_t target_wwn_product_id_store(struct config_item *item,
>  	/* +2 to allow for a trailing (stripped) '\n' and null-terminator */
>  	unsigned char buf[INQUIRY_MODEL_LEN + 2];
>  	char *stripped = NULL;
> -	size_t len;
> +	ssize_t len;
>  	ssize_t ret;
> 
> -	len = strlcpy(buf, page, sizeof(buf));
> -	if (len < sizeof(buf)) {
> +	len = strscpy(buf, page, sizeof(buf));
> +	if (len > 0) {
>  		/* Strip any newline added from userspace. */
>  		stripped = strstrip(buf);
> -		len = strlen(stripped);
>  	}
> -	if (len > INQUIRY_MODEL_LEN) {
> +	if (len < 0 || strlen(stripped) > INQUIRY_MODEL_LEN) {
>  		pr_err("Emulated T10 Vendor exceeds INQUIRY_MODEL_LEN: "
>  			 __stringify(INQUIRY_MODEL_LEN)
>  			"\n");
> @@ -1504,16 +1502,15 @@ static ssize_t target_wwn_revision_store(struct config_item *item,
>  	/* +2 to allow for a trailing (stripped) '\n' and null-terminator */
>  	unsigned char buf[INQUIRY_REVISION_LEN + 2];
>  	char *stripped = NULL;
> -	size_t len;
> +	ssize_t len;
>  	ssize_t ret;
> 
> -	len = strlcpy(buf, page, sizeof(buf));
> -	if (len < sizeof(buf)) {
> +	len = strscpy(buf, page, sizeof(buf));
> +	if (len > 0) {
>  		/* Strip any newline added from userspace. */
>  		stripped = strstrip(buf);
> -		len = strlen(stripped);
>  	}
> -	if (len > INQUIRY_REVISION_LEN) {
> +	if (len < 0 || strlen(stripped) > INQUIRY_REVISION_LEN) {
>  		pr_err("Emulated T10 Revision exceeds INQUIRY_REVISION_LEN: "
>  			 __stringify(INQUIRY_REVISION_LEN)
>  			"\n");
> --
> 2.42.0.283.g2d96d420d3-goog
> 
>
Kees Cook Aug. 30, 2023, 10:40 p.m. UTC | #4 
On Wed, Aug 30, 2023 at 09:53:30PM +0000, Justin Stitt wrote:
> On Wed, Aug 30, 2023 at 09:07:24PM +0000, Azeem Shaikh wrote:
> > strlcpy() reads the entire source buffer first.
> > This read may exceed the destination size limit.
> > This is both inefficient and can lead to linear read
> > overflows if a source string is not NUL-terminated [1].
> > In an effort to remove strlcpy() completely [2], replace
> > strlcpy() here with strscpy().
> >
> > Direct replacement is safe here since return value of -errno
> > is used to check for truncation instead of sizeof(dest).
> >
> > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> > [2] https://github.com/KSPP/linux/issues/89
> >
> > Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
> > ---
> > v2:
> >  * Replace all instances of strlcpy in this file instead of just 1.
> >
> > v1:
> >  * https://lore.kernel.org/all/20230830200717.4129442-1-azeemshaikh38@gmail.com/
> >
> >  drivers/target/target_core_configfs.c |   27 ++++++++++++---------------
> >  1 file changed, 12 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
> > index 936e5ff1b209..10a22a428267 100644
> > --- a/drivers/target/target_core_configfs.c
> > +++ b/drivers/target/target_core_configfs.c
> > @@ -1392,16 +1392,15 @@ static ssize_t target_wwn_vendor_id_store(struct config_item *item,
> >  	/* +2 to allow for a trailing (stripped) '\n' and null-terminator */
> >  	unsigned char buf[INQUIRY_VENDOR_LEN + 2];
> >  	char *stripped = NULL;
> > -	size_t len;
> > +	ssize_t len;
> >  	ssize_t ret;
> >
> > -	len = strlcpy(buf, page, sizeof(buf));
> > -	if (len < sizeof(buf)) {
> > +	len = strscpy(buf, page, sizeof(buf));
> > +	if (len > 0) {
> >  		/* Strip any newline added from userspace. */
> >  		stripped = strstrip(buf);
> > -		len = strlen(stripped);
> >  	}
> > -	if (len > INQUIRY_VENDOR_LEN) {
> > +	if (len < 0 || strlen(stripped) > INQUIRY_VENDOR_LEN) {
> >  		pr_err("Emulated T10 Vendor Identification exceeds"
> >  			" INQUIRY_VENDOR_LEN: " __stringify(INQUIRY_VENDOR_LEN)
> >  			"\n");
> 
> Should we be explicitly checking for `len == -E2BIG` instead of the more
> generic `len < 0`? Perhaps this is a nitpick but I prefer the former.

For robustness, we want to just do the "< 0" test -- that way if
strscpy() gains a new errno (for some unimaginable reason) then all the
code testing for "< 0" will continue to work sanely.

-Kees
diff mbox series

Patch

diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
index 936e5ff1b209..10a22a428267 100644
--- a/drivers/target/target_core_configfs.c
+++ b/drivers/target/target_core_configfs.c
@@ -1392,16 +1392,15 @@  static ssize_t target_wwn_vendor_id_store(struct config_item *item,
 	/* +2 to allow for a trailing (stripped) '\n' and null-terminator */
 	unsigned char buf[INQUIRY_VENDOR_LEN + 2];
 	char *stripped = NULL;
-	size_t len;
+	ssize_t len;
 	ssize_t ret;

-	len = strlcpy(buf, page, sizeof(buf));
-	if (len < sizeof(buf)) {
+	len = strscpy(buf, page, sizeof(buf));
+	if (len > 0) {
 		/* Strip any newline added from userspace. */
 		stripped = strstrip(buf);
-		len = strlen(stripped);
 	}
-	if (len > INQUIRY_VENDOR_LEN) {
+	if (len < 0 || strlen(stripped) > INQUIRY_VENDOR_LEN) {
 		pr_err("Emulated T10 Vendor Identification exceeds"
 			" INQUIRY_VENDOR_LEN: " __stringify(INQUIRY_VENDOR_LEN)
 			"\n");
@@ -1448,16 +1447,15 @@  static ssize_t target_wwn_product_id_store(struct config_item *item,
 	/* +2 to allow for a trailing (stripped) '\n' and null-terminator */
 	unsigned char buf[INQUIRY_MODEL_LEN + 2];
 	char *stripped = NULL;
-	size_t len;
+	ssize_t len;
 	ssize_t ret;

-	len = strlcpy(buf, page, sizeof(buf));
-	if (len < sizeof(buf)) {
+	len = strscpy(buf, page, sizeof(buf));
+	if (len > 0) {
 		/* Strip any newline added from userspace. */
 		stripped = strstrip(buf);
-		len = strlen(stripped);
 	}
-	if (len > INQUIRY_MODEL_LEN) {
+	if (len < 0 || strlen(stripped) > INQUIRY_MODEL_LEN) {
 		pr_err("Emulated T10 Vendor exceeds INQUIRY_MODEL_LEN: "
 			 __stringify(INQUIRY_MODEL_LEN)
 			"\n");
@@ -1504,16 +1502,15 @@  static ssize_t target_wwn_revision_store(struct config_item *item,
 	/* +2 to allow for a trailing (stripped) '\n' and null-terminator */
 	unsigned char buf[INQUIRY_REVISION_LEN + 2];
 	char *stripped = NULL;
-	size_t len;
+	ssize_t len;
 	ssize_t ret;

-	len = strlcpy(buf, page, sizeof(buf));
-	if (len < sizeof(buf)) {
+	len = strscpy(buf, page, sizeof(buf));
+	if (len > 0) {
 		/* Strip any newline added from userspace. */
 		stripped = strstrip(buf);
-		len = strlen(stripped);
 	}
-	if (len > INQUIRY_REVISION_LEN) {
+	if (len < 0 || strlen(stripped) > INQUIRY_REVISION_LEN) {
 		pr_err("Emulated T10 Revision exceeds INQUIRY_REVISION_LEN: "
 			 __stringify(INQUIRY_REVISION_LEN)
 			"\n");