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Sun, 11 Oct 2026 08:09:22 -0700 (PDT) Sender: Julian Braha Message-ID: Date: Sun, 11 Oct 2026 16:09:21 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] kconfig: fix dangling check_top after an unexpected recursive dependency To: Leizhen Zhang , nathan@kernel.org, nsc@kernel.org Cc: linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org References: <20261008164528.3685545-1-lzsx618@gmail.com> Content-Language: en-US From: Julian Braha In-Reply-To: <20261008164528.3685545-1-lzsx618@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/8/26 17:45, Leizhen Zhang wrote: > If the last symbol of a recursive dependency is a choice value, > sym_check_print_recursive() pushes the on-stack cv_stack onto the > dependency stack. If the choice is then not found on the stack, the > function prints "unexpected recursive dependency error" and returns > without removing cv_stack again. check_top is left pointing into the > stack frame of the returned function, and the next dep_stack_remove() > dereferences it: > > AddressSanitizer: stack-use-after-return ... in dep_stack_remove > > This can be triggered by an (invalid) Kconfig file in which a symbol is > a choice value of two choices and the second choice depends on it: > > choice > prompt "c1" > config A > bool "a" > endchoice > > choice > prompt "c2" > depends on A > config A > bool "a" > endchoice > > Jump to the existing cleanup at the end of the function instead of > returning directly. > > Found by fuzzing Kconfig input with ASan/UBSan. > > Fixes: d595cea62403 ("kconfig: print more info when we see a recursive dependency") > Assisted-by: Claude:claude-opus-5-5 ASan UBSan libFuzzer > Signed-off-by: Leizhen Zhang Reviewed-by: Julian Braha