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Message-ID: <202310081009.045F3E99@keescook> Date: Sun, 8 Oct 2023 10:12:01 -0700 From: Kees Cook <keescook@...omium.org> To: Christophe JAILLET <christophe.jaillet@...adoo.fr> Cc: 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>, "Gustavo A. R. Silva" <gustavoars@...nel.org>, Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org, linux-hardening@...r.kernel.org, llvm@...ts.linux.dev Subject: Re: [PATCH] VMCI: Annotate struct vmci_handle_arr with __counted_by On Sat, Oct 07, 2023 at 04:32:34PM +0200, Christophe JAILLET wrote: > 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(). I think this should likely lose VMCI_HANDLE_ARRAY_HEADER_SIZE entirely and the helper to use sizeof() and struct_size() directly, but probably as a separate patch. > > Note that I'm slightly unsure on how things will behave in regards to the > krealloc() in vmci_handle_arr_append_entry(). It looks correct to me: new_array = krealloc(array, new_size, GFP_ATOMIC); ... new_array->capacity += capacity_bump; i.e. "capacity" is adjusted up before accessing any "entries". > > [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 > Reviewed-by: Kees Cook <keescook@...omium.org> -- Kees Cook
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