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virtio_console: Annotate struct port_buffer with __counted_by

PATCH Applied Kees Cook 3 participants 4 messages Sep 22, 2023 – Oct 24, 2023

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Char and misc drivers virtio core virtio console driver
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Kees Cook

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#0 lore raw

PATCH 1/1 virtio_console: Annotate struct port_buffer with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by attribute. Flexible array members annotated with __counted_by can have their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions).

As found with Coccinelle[1], add __counted_by for struct port_buffer.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc Amit Shah <[email protected]>
Cc Arnd Bergmann <[email protected]>
Cc Greg Kroah-Hartman <[email protected]>
Cc [email protected]
Signed-off-by Kees Cook <[email protected]>
---
 drivers/char/virtio_console.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
drivers/char/virtio_console.c +1 -1
index 680d1ef2a217..431e9e5bf9c1 100644
@@ -106,7 +106,7 @@ struct port_buffer {
 	unsigned int sgpages;
 
 	/* sg is used if spages > 0. sg must be the last in is struct */
-	struct scatterlist sg[];
+	struct scatterlist sg[] __counted_by(sgpages);
 };
 
 /*
Signature · 1 line
2.34.1
Reviewed-by on v1 1/1
#1 lore raw
Quoted 8 lines · Kees Cook

Prepare for the coming implementation by GCC and Clang of the __counted_by attribute. Flexible array members annotated with __counted_by can have their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions).

As found with Coccinelle[1], add __counted_by for struct port_buffer.

Quoted 7 lines

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc Amit Shah <[email protected]>
Cc Arnd Bergmann <[email protected]>
Cc Greg Kroah-Hartman <[email protected]>
Cc [email protected]
Signed-off-by Kees Cook <[email protected]>
Reviewed-by Gustavo A. R. Silva <[email protected]>

Thanks

Signature · 1 line
Gustavo
Quoted 17 lines
---
  drivers/char/virtio_console.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)
drivers/char/virtio_console.c +1 -1
index 680d1ef2a217..431e9e5bf9c1 100644
@@ -106,7 +106,7 @@ struct port_buffer {
  	unsigned int sgpages;
 
  	/* sg is used if spages > 0. sg must be the last in is struct */
-	struct scatterlist sg[];
+	struct scatterlist sg[] __counted_by(sgpages);
  };
 
  /*
Reviewed-by on v1 1/1
#2 lore raw
In reply to Kees Cook
Quoted 24 lines · Kees Cook

Prepare for the coming implementation by GCC and Clang of the __counted_by attribute. Flexible array members annotated with __counted_by can have their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions).

As found with Coccinelle[1], add __counted_by for struct port_buffer.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc Amit Shah <[email protected]>
Cc Arnd Bergmann <[email protected]>
Cc Greg Kroah-Hartman <[email protected]>
Cc [email protected]
Signed-off-by Kees Cook <[email protected]>
---
 drivers/char/virtio_console.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
drivers/char/virtio_console.c +0 -0
index 680d1ef2a217..431e9e5bf9c1 100644

drivers/char/virtio_console.c struct port_buffer { · line 110

Quoted 6 lines
drivers/char/virtio_console.c +1 -1
@@ -106,7 +106,7 @@ struct port_buffer {
 	unsigned int sgpages;
 
 	/* sg is used if spages > 0. sg must be the last in is struct */
-	struct scatterlist sg[];
+	struct scatterlist sg[] __counted_by(sgpages);
 };
Reviewed-by Amit Shah <[email protected]>

Greg, please pick this up.

Thanks,

Amit

author Applied
#3 lore raw
In reply to Kees Cook
Quoted 9 lines · Kees Cook

Prepare for the coming implementation by GCC and Clang of the __counted_by attribute. Flexible array members annotated with __counted_by can have their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions).

As found with Coccinelle[1], add __counted_by for struct port_buffer.

[...]

Applied to for-next/hardening, thanks!

[1/1] virtio_console: Annotate struct port_buffer with __counted_by

      https://git.kernel.org/kees/c/bf5abc17bc43

Take care,

Signature · 1 line
Kees Cook