[PATCH] scsi: libfc: Fix potential buffer overflow in fc_ct_ms_fill()

[PATCH] scsi: libfc: Fix potential buffer overflow in fc_ct_ms_fill()

[Alok Tiwari]

The fc_ct_ms_fill() helper currently formats the OS name and version
into entry->value using "%s v%s". Since init_utsname()->sysname and
->release are unbounded strings, snprintf() may attempt to write more
than FC_FDMI_HBA_ATTR_OSNAMEVERSION_LEN bytes, triggering a
-Wformat-truncation warning with W=1.

In file included from drivers/scsi/libfc/fc_elsct.c:18:
drivers/scsi/libfc/fc_encode.h: In function ‘fc_ct_ms_fill.constprop’:
drivers/scsi/libfc/fc_encode.h:359:30: error: ‘%s’ directive output may
be truncated writing up to 64 bytes into a region of size between 62
and 126 [-Werror=format-truncation=]
  359 |                         "%s v%s",
      |                              ^~
  360 |                         init_utsname()->sysname,
  361 |                         init_utsname()->release);
      |                         ~~~~~~~~~~~~~~~~~~~~~~~
drivers/scsi/libfc/fc_encode.h:357:17: note: ‘snprintf’ output between
3 and 131 bytes into a destination of size 128
  357 |                 snprintf((char *)&entry->value,
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  358 |                         FC_FDMI_HBA_ATTR_OSNAMEVERSION_LEN,
      |                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  359 |                         "%s v%s",
      |                         ~~~~~~~~~
  360 |                         init_utsname()->sysname,
      |                         ~~~~~~~~~~~~~~~~~~~~~~~~
  361 |                         init_utsname()->release);
      |                         ~~~~~~~~~~~~~~~~~~~~~~~~

Fix this by using "%.62s v%.62s", which ensures both sysname and
release are truncated to fit within the 64-byte field defined by
FC_FDMI_HBA_ATTR_OSNAMEVERSION_LEN.

Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>
---
 drivers/scsi/libfc/fc_encode.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/libfc/fc_encode.h b/drivers/scsi/libfc/fc_encode.h
index 02e31db31d68..e046091a549a 100644
--- a/drivers/scsi/libfc/fc_encode.h
+++ b/drivers/scsi/libfc/fc_encode.h
@@ -356,7 +356,7 @@ static inline int fc_ct_ms_fill(struct fc_lport *lport,
 		put_unaligned_be16(len, &entry->len);
 		snprintf((char *)&entry->value,
 			FC_FDMI_HBA_ATTR_OSNAMEVERSION_LEN,
-			"%s v%s",
+			"%.62s v%.62s",
 			init_utsname()->sysname,
 			init_utsname()->release);
 
-- 
2.50.1

Re: [PATCH] scsi: libfc: Fix potential buffer overflow in fc_ct_ms_fill()

[Martin K. Petersen]

Alok,

> The fc_ct_ms_fill() helper currently formats the OS name and version
> into entry->value using "%s v%s". Since init_utsname()->sysname and
> ->release are unbounded strings, snprintf() may attempt to write more
> than FC_FDMI_HBA_ATTR_OSNAMEVERSION_LEN bytes, triggering a
> -Wformat-truncation warning with W=1.

Applied to 6.18/scsi-staging, thanks!

-- 
Martin K. Petersen

Re: [PATCH] scsi: libfc: Fix potential buffer overflow in fc_ct_ms_fill()

[Martin K. Petersen]

On Mon, 15 Sep 2025 11:37:57 -0700, Alok Tiwari wrote:

> The fc_ct_ms_fill() helper currently formats the OS name and version
> into entry->value using "%s v%s". Since init_utsname()->sysname and
> ->release are unbounded strings, snprintf() may attempt to write more
> than FC_FDMI_HBA_ATTR_OSNAMEVERSION_LEN bytes, triggering a
> -Wformat-truncation warning with W=1.
> 
> In file included from drivers/scsi/libfc/fc_elsct.c:18:
> drivers/scsi/libfc/fc_encode.h: In function ‘fc_ct_ms_fill.constprop’:
> drivers/scsi/libfc/fc_encode.h:359:30: error: ‘%s’ directive output may
> be truncated writing up to 64 bytes into a region of size between 62
> and 126 [-Werror=format-truncation=]
>   359 |                         "%s v%s",
>       |                              ^~
>   360 |                         init_utsname()->sysname,
>   361 |                         init_utsname()->release);
>       |                         ~~~~~~~~~~~~~~~~~~~~~~~
> drivers/scsi/libfc/fc_encode.h:357:17: note: ‘snprintf’ output between
> 3 and 131 bytes into a destination of size 128
>   357 |                 snprintf((char *)&entry->value,
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   358 |                         FC_FDMI_HBA_ATTR_OSNAMEVERSION_LEN,
>       |                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   359 |                         "%s v%s",
>       |                         ~~~~~~~~~
>   360 |                         init_utsname()->sysname,
>       |                         ~~~~~~~~~~~~~~~~~~~~~~~~
>   361 |                         init_utsname()->release);
>       |                         ~~~~~~~~~~~~~~~~~~~~~~~~
> 
> [...]

Applied to 6.18/scsi-queue, thanks!

[1/1] scsi: libfc: Fix potential buffer overflow in fc_ct_ms_fill()
      https://git.kernel.org/mkp/scsi/c/072fdd4b0be9

-- 
Martin K. Petersen