diff mbox series

[v3] scsi: target: Replace strlcpy with strscpy

Message ID 20230831143638.232596-1-azeemshaikh38@gmail.com (mailing list archive)
State Accepted
Commit 5c584fe6098ae1727650acbabdef0669cefec7be
Headers show
Series [v3] scsi: target: Replace strlcpy with strscpy | expand

Commit Message

Azeem Shaikh Aug. 31, 2023, 2:36 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>
---
v3:
 * Address readability comment.

v2:
 * Replace all instances of strlcpy in this file instead of just 1.
 * https://lore.kernel.org/all/20230830210724.4156575-1-azeemshaikh38@gmail.com/

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

 drivers/target/target_core_configfs.c |   24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

--
2.42.0.283.g2d96d420d3-goog

Comments

Kees Cook Aug. 31, 2023, 6:42 p.m. UTC | #1 
On Thu, Aug 31, 2023 at 02:36:38PM +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>
> ---
> v3:
>  * Address readability comment.
> 
> v2:
>  * Replace all instances of strlcpy in this file instead of just 1.
>  * https://lore.kernel.org/all/20230830210724.4156575-1-azeemshaikh38@gmail.com/
> 
> v1:
>  * https://lore.kernel.org/all/20230830200717.4129442-1-azeemshaikh38@gmail.com/
> 
>  drivers/target/target_core_configfs.c |   24 ++++++++++++------------
>  1 file changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
> index 936e5ff1b209..d5860c1c1f46 100644
> --- a/drivers/target/target_core_configfs.c
> +++ b/drivers/target/target_core_configfs.c
> @@ -1392,16 +1392,16 @@ 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 || len > INQUIRY_VENDOR_LEN) {

Agh, sorry I missed this before: the first "if" needs to be "len >= 0"
otherwise this:

        ret = target_check_inquiry_data(stripped);

will be passing a NULL pointer...
Azeem Shaikh Aug. 31, 2023, 7:20 p.m. UTC | #2 
On Thu, Aug 31, 2023 at 2:42 PM Kees Cook <keescook@chromium.org> wrote:
>
> On Thu, Aug 31, 2023 at 02:36:38PM +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>
> > ---
> > v3:
> >  * Address readability comment.
> >
> > v2:
> >  * Replace all instances of strlcpy in this file instead of just 1.
> >  * https://lore.kernel.org/all/20230830210724.4156575-1-azeemshaikh38@gmail.com/
> >
> > v1:
> >  * https://lore.kernel.org/all/20230830200717.4129442-1-azeemshaikh38@gmail.com/
> >
> >  drivers/target/target_core_configfs.c |   24 ++++++++++++------------
> >  1 file changed, 12 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
> > index 936e5ff1b209..d5860c1c1f46 100644
> > --- a/drivers/target/target_core_configfs.c
> > +++ b/drivers/target/target_core_configfs.c
> > @@ -1392,16 +1392,16 @@ 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 || len > INQUIRY_VENDOR_LEN) {
>
> Agh, sorry I missed this before: the first "if" needs to be "len >= 0"
> otherwise this:
>
>         ret = target_check_inquiry_data(stripped);
>
> will be passing a NULL pointer...
>

Hmm, the current implementation of strscpy never returns 0. If
sizeof(buf) is 0, it'll return -E2BIG. Do you still prefer that I
update this to check for len >= 0?
Kees Cook Aug. 31, 2023, 9:02 p.m. UTC | #3 
On Thu, Aug 31, 2023 at 03:20:47PM -0400, Azeem Shaikh wrote:
> On Thu, Aug 31, 2023 at 2:42 PM Kees Cook <keescook@chromium.org> wrote:
> >
> > On Thu, Aug 31, 2023 at 02:36:38PM +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>
> > > ---
> > > v3:
> > >  * Address readability comment.
> > >
> > > v2:
> > >  * Replace all instances of strlcpy in this file instead of just 1.
> > >  * https://lore.kernel.org/all/20230830210724.4156575-1-azeemshaikh38@gmail.com/
> > >
> > > v1:
> > >  * https://lore.kernel.org/all/20230830200717.4129442-1-azeemshaikh38@gmail.com/
> > >
> > >  drivers/target/target_core_configfs.c |   24 ++++++++++++------------
> > >  1 file changed, 12 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
> > > index 936e5ff1b209..d5860c1c1f46 100644
> > > --- a/drivers/target/target_core_configfs.c
> > > +++ b/drivers/target/target_core_configfs.c
> > > @@ -1392,16 +1392,16 @@ 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 || len > INQUIRY_VENDOR_LEN) {
> >
> > Agh, sorry I missed this before: the first "if" needs to be "len >= 0"
> > otherwise this:
> >
> >         ret = target_check_inquiry_data(stripped);
> >
> > will be passing a NULL pointer...
> >
> 
> Hmm, the current implementation of strscpy never returns 0. If
> sizeof(buf) is 0, it'll return -E2BIG. Do you still prefer that I
> update this to check for len >= 0?

Oh right! Nevermind, then. Fine as-is. :)

Reviewed-by: Kees Cook <keescook@chromium.org>
Martin K. Petersen Sept. 5, 2023, 9:56 a.m. UTC | #4 
Azeem,

> 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().

Applied to 6.6/scsi-staging, thanks!
Martin K. Petersen Sept. 14, 2023, 1:40 a.m. UTC | #5 
On Thu, 31 Aug 2023 14:36:38 +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().
> 
> [...]

Applied to 6.6/scsi-fixes, thanks!

[1/1] scsi: target: Replace strlcpy with strscpy
      https://git.kernel.org/mkp/scsi/c/5c584fe6098a
diff mbox series

Patch

diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
index 936e5ff1b209..d5860c1c1f46 100644
--- a/drivers/target/target_core_configfs.c
+++ b/drivers/target/target_core_configfs.c
@@ -1392,16 +1392,16 @@  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 || len > INQUIRY_VENDOR_LEN) {
 		pr_err("Emulated T10 Vendor Identification exceeds"
 			" INQUIRY_VENDOR_LEN: " __stringify(INQUIRY_VENDOR_LEN)
 			"\n");
@@ -1448,16 +1448,16 @@  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 || len > INQUIRY_MODEL_LEN) {
 		pr_err("Emulated T10 Vendor exceeds INQUIRY_MODEL_LEN: "
 			 __stringify(INQUIRY_MODEL_LEN)
 			"\n");
@@ -1504,16 +1504,16 @@  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 || len > INQUIRY_REVISION_LEN) {
 		pr_err("Emulated T10 Revision exceeds INQUIRY_REVISION_LEN: "
 			 __stringify(INQUIRY_REVISION_LEN)
 			"\n");