linux-hardening - [PATCH] VMCI: Annotate struct vmci_handle_arr with __counted

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Date: Sat,  7 Oct 2023 16:32:34 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Bryan Tan <bryantan@...are.com>,
	Vishnu Dasa <vdasa@...are.com>,
	VMware PV-Drivers Reviewers <pv-drivers@...are.com>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Kees Cook <keescook@...omium.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Tom Rix <trix@...hat.com>
Cc: linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>,
	linux-hardening@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH] VMCI: Annotate struct vmci_handle_arr 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).

Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
This patch is part of a work done in parallel of what is currently worked
on by Kees Cook.

My patches are only related to corner cases that do NOT match the
semantic of his Coccinelle script[1].

In this case, something similar to struct_size() is implemented in
handle_arr_calc_size().

Note that I'm slightly unsure on how things will behave in regards to the
krealloc() in vmci_handle_arr_append_entry().

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
---
 drivers/misc/vmw_vmci/vmci_handle_array.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/misc/vmw_vmci/vmci_handle_array.h b/drivers/misc/vmw_vmci/vmci_handle_array.h
index 96193f85be5b..b0e6b1956014 100644
--- a/drivers/misc/vmw_vmci/vmci_handle_array.h
+++ b/drivers/misc/vmw_vmci/vmci_handle_array.h
@@ -17,7 +17,7 @@ struct vmci_handle_arr {
 	u32 max_capacity;
 	u32 size;
 	u32 pad;
-	struct vmci_handle entries[];
+	struct vmci_handle entries[] __counted_by(capacity);
 };
 
 #define VMCI_HANDLE_ARRAY_HEADER_SIZE				\
-- 
2.34.1