Re: [PATCH] scsi: elx: libefc: Fix second parameter type in state callbacks

From: Kees Cook <keescook@chromium.org>
To: Nathan Chancellor <nathan@kernel.org>
Cc: James Smart <james.smart@broadcom.com>,
	Ram Vegesna <ram.vegesna@broadcom.com>,
	"James E.J. Bottomley" <jejb@linux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	linux-scsi@vger.kernel.org, target-devel@vger.kernel.org,
	Nick Desaulniers <ndesaulniers@google.com>,
	Tom Rix <trix@redhat.com>,
	Sami Tolvanen <samitolvanen@google.com>,
	llvm@lists.linux.dev, linux-kernel@vger.kernel.org,
	patches@lists.linux.dev
Subject: Re: [PATCH] scsi: elx: libefc: Fix second parameter type in state callbacks
Date: Wed, 2 Nov 2022 12:08:30 -0700	[thread overview]
Message-ID: <202211021208.055D396D8E@keescook> (raw)
In-Reply-To: <20221102161906.2781508-1-nathan@kernel.org>

On Wed, Nov 02, 2022 at 09:19:06AM -0700, Nathan Chancellor wrote:
> With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG),
> indirect call targets are validated against the expected function
> pointer prototype to make sure the call target is valid to help mitigate
> ROP attacks. If they are not identical, there is a failure at run time,
> which manifests as either a kernel panic or thread getting killed. A
> proposed warning in clang aims to catch these at compile time, which
> reveals:
> 
>   drivers/scsi/elx/libefc/efc_node.c:811:22: error: incompatible function pointer types assigning to 'void (*)(struct efc_sm_ctx *, u32, void *)' (aka 'void (*)(struct efc_sm_ctx *, unsigned int, void *)') from 'void (*)(struct efc_sm_ctx *, enum efc_sm_event, void *)' [-Werror,-Wincompatible-function-pointer-types-strict]
>                   ctx->current_state = state;
>                                     ^ ~~~~~
>   drivers/scsi/elx/libefc/efc_node.c:878:21: error: incompatible function pointer types assigning to 'void (*)(struct efc_sm_ctx *, u32, void *)' (aka 'void (*)(struct efc_sm_ctx *, unsigned int, void *)') from 'void (*)(struct efc_sm_ctx *, enum efc_sm_event, void *)' [-Werror,-Wincompatible-function-pointer-types-strict]
>           node->nodedb_state = state;
>                             ^ ~~~~~
>   drivers/scsi/elx/libefc/efc_node.c:905:6: error: incompatible function pointer types assigning to 'void (*)(struct efc_sm_ctx *, enum efc_sm_event, void *)' from 'void (*)(struct efc_sm_ctx *, u32, void *)' (aka 'void (*)(struct efc_sm_ctx *, unsigned int, void *)') [-Werror,-Wincompatible-function-pointer-types-strict]
>                   pf = node->nodedb_state;
>                     ^ ~~~~~~~~~~~~~~~~~~
> 
>   drivers/scsi/elx/libefc/efc_device.c:455:22: error: incompatible function pointer types assigning to 'void (*)(struct efc_sm_ctx *, u32, void *)' (aka 'void (*)(struct efc_sm_ctx *, unsigned int, void *)') from 'void (struct efc_sm_ctx *, enum efc_sm_event, void *)' [-Werror,-Wincompatible-function-pointer-types-strict]
>                   node->nodedb_state = __efc_d_init;
>                                     ^ ~~~~~~~~~~~~
> 
>   drivers/scsi/elx/libefc/efc_sm.c:41:22: error: incompatible function pointer types assigning to 'void (*)(struct efc_sm_ctx *, u32, void *)' (aka 'void (*)(struct efc_sm_ctx *, unsigned int, void *)') from 'void (*)(struct efc_sm_ctx *, enum efc_sm_event, void *)' [-Werror,-Wincompatible-function-pointer-types-strict]
>                   ctx->current_state = state;
>                                     ^ ~~~~~
> 
> The type of the second parameter in the prototypes of ->current_state()
> and ->nodedb_state() ('u32') does not match the implementations, which
> have a second parameter type of 'enum efc_sm_event'. Update the
> prototypes to have the correct second parameter type, clearing up all
> the warnings and CFI failures.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/1750
> Reported-by: Sami Tolvanen <samitolvanen@google.com>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook