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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47795268e0asm9388645e9.6.2025.11.14.06.31.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 14 Nov 2025 06:31:08 -0800 (PST) Date: Fri, 14 Nov 2025 14:31:04 +0000 From: David Laight To: Steven Rostedt Cc: Thorsten Blum , Josh Poimboeuf , Kees Cook , "Gustavo A. R. Silva" , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] unwind deferred: Annotate struct unwind_cache with __counted_by Message-ID: <20251114143104.0d1aead3@pumpkin> In-Reply-To: <20251114084346.6469edc0@gandalf.local.home> References: <20251114122748.222833-1-thorsten.blum@linux.dev> <20251114084346.6469edc0@gandalf.local.home> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 14 Nov 2025 08:43:46 -0500 Steven Rostedt wrote: > On Fri, 14 Nov 2025 13:27:47 +0100 > Thorsten Blum wrote: > > > Add the __counted_by() compiler attribute to the flexible array member > > 'entries' to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and > > CONFIG_FORTIFY_SOURCE. > > > > Signed-off-by: Thorsten Blum > > --- > > include/linux/unwind_deferred_types.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/include/linux/unwind_deferred_types.h b/include/linux/unwind_deferred_types.h > > index 33b62ac25c86..d4b67f0116f3 100644 > > --- a/include/linux/unwind_deferred_types.h > > +++ b/include/linux/unwind_deferred_types.h > > @@ -5,7 +5,7 @@ > > struct unwind_cache { > > unsigned long unwind_completed; > > unsigned int nr_entries; > > - unsigned long entries[]; > > + unsigned long entries[] __counted_by(nr_entries); > > }; > > > > /* > > Wrong! > > I need to add a comment here that entries is not bound by nr_entries. > > https://lore.kernel.org/all/20250730093249.4833be14@gandalf.local.home/ > > Maybe this?: > > diff --git a/include/linux/unwind_deferred_types.h b/include/linux/unwind_deferred_types.h > index 33b62ac25c86..d05409bb14fa 100644 > --- a/include/linux/unwind_deferred_types.h > +++ b/include/linux/unwind_deferred_types.h > @@ -5,7 +5,7 @@ > struct unwind_cache { > unsigned long unwind_completed; Does that need to be 'long' - 'int' would fit in the padding on 64bit. > unsigned int nr_entries; > - unsigned long entries[]; > + unsigned long entries[]; /* Fixed size, not bound by nr_entries */ > }; Perhaps it should be: unsigned long entries[ /* MAX_UNWIND_ENTRIES */ ]; David > > /* > > > > -- Steve >