From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7B0F037DEAA for ; Thu, 18 Jun 2026 05:12:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781759576; cv=none; b=elFP7iR3/SHw/zlAgHms/S+2V/dt406ILKKgJ8gMyZnyRw76RLTddiB0iY7BrGZsoWolU910XDnjHL1lH+AdDzU/PcTsyE6exKDQZpYIiD4dHSSDJeM1+8oBmLlOX9w/4fFspJvbgeOk1EuDuRpbK/561EDKCLnKV5vWAxzQl9Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781759576; c=relaxed/simple; bh=ARmXfzfmk3LT7n9bbeg9IGAGgbAhu0IwTEMKbxCVmCM=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=lxPQPu50Cwh+OxUtEGJiIYqg9K28ps7arUJteklaINVlfpSS+GHLwmdxE/QV8lcHowl3wdiOasCekuVzohJyPUlbsy3XcGXwZJvig/7MQ3cViSw42GnWmkecIXAIA2vW4bP1FPRtCg657yML2xJ64H0v+dRfJYk3AYQxts+6klk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Sm9DrOkQ; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Sm9DrOkQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2C2431F000E9; Thu, 18 Jun 2026 05:12:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781759575; bh=bz8rcJEvW+UYdjiZC8i4NMtHtvVIsO82vzYqLQfHPok=; h=From:To:Cc:Subject:Date; b=Sm9DrOkQTvyuC0AqtzBB/KQawv7JeaFfGx8YbTCrYAU5cm3XSQAv3YxPJ8BqK/fj0 DH8dtqQNXFsgDc7p1FjWSBBVP/IUfQdSGdc8n4GpwsmJ0ZZt1nd8jwPoCsUD0wYckl HH1ja0+M4iK7b8P4xMCfMqGQh4jZxy2nGsY2nMOYSk/wb/NikCaqEnUeaEMtokjNHu /00U6vsAa68ZJjo92/wJE1TblyZFawQ/OgAA+0gfam4eqewBHFEJQDTZtgOYM/S2f8 QFWAXyrjTJAUUg+OEI23Fot5YoxhrOtkIGlGaf2wKwnlHIlx8XitOspgca9Bs3GYBp 7/pWOkqJlbGbg== From: Kees Cook To: Martin Uecker Cc: Kees Cook , Richard Biener , gcc-patches@gcc.gnu.org, linux-hardening@vger.kernel.org Subject: [PATCH] c: handle .ACCESS_WITH_SIZE in build_unary_op for !/+/- [PR123569] Date: Wed, 17 Jun 2026 22:12:51 -0700 Message-Id: <20260618051246.work.269-kees@kernel.org> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4010; i=kees@kernel.org; h=from:subject:message-id; bh=ARmXfzfmk3LT7n9bbeg9IGAGgbAhu0IwTEMKbxCVmCM=; b=owGbwMvMwCVmps19z/KJym7G02pJDFnGdcFvVu+7svcqQ1IJ96mKxEkal8/eW72Apfkvq/anx A/LvMMEO0pZGMS4GGTFFFmC7NzjXDzetoe7z1WEmcPKBDKEgYtTACYSI8PI0MThox31SpP98uG6 pnjRqN/FE/5+3sgWyCydZCjVPHO7IcM/xatxC9kvnXo2ZbraVxuec96p7PfnPrE6x5A4Pa7H60o RDwA= X-Developer-Key: i=kees@kernel.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit PR123569 fixed wrong code with the counted_by attribute on a pointer member by suppressing creation of the .ACCESS_WITH_SIZE wrapper in the parser's pre/post-increment paths, and added a checking assertion in build_unary_op to ensure no .ACCESS_WITH_SIZE call reaches it. The other rvalue-consuming unary operators (!, -, +) still rvalue-convert their operand via convert_lvalue_to_rvalue, which produces the .ACCESS_WITH_SIZE wrapper as before. They then reach parser_build_unary_op then build_unary_op carrying the wrapper and trip the assertion. A minimal reproducer: struct s { int n; char *p __attribute__((__counted_by__(n))); }; int f (struct s *o) { return !o->p; } Unwrap the .ACCESS_WITH_SIZE call at the top of build_unary_op via get_ref_from_access_with_size. These unary operators consume the pointer rvalue rather than the pointed-to data, so the bounds-checking wrapper is not useful here. The assertion is retained: after the unwrap it documents the post-condition the rest of the function relies on. PR c/123569 gcc/c/ChangeLog: * c-typeck.cc (build_unary_op): Unwrap .ACCESS_WITH_SIZE from the operand before further processing. gcc/testsuite/ChangeLog: * gcc.dg/counted-by-unary.c: New test. --- gcc/testsuite/gcc.dg/counted-by-unary.c | 32 +++++++++++++++++++++++++ gcc/c/c-typeck.cc | 12 ++++++++++ 2 files changed, 44 insertions(+) create mode 100644 gcc/testsuite/gcc.dg/counted-by-unary.c diff --git a/gcc/testsuite/gcc.dg/counted-by-unary.c b/gcc/testsuite/gcc.dg/counted-by-unary.c new file mode 100644 index 000000000000..b16b819d63b6 --- /dev/null +++ b/gcc/testsuite/gcc.dg/counted-by-unary.c @@ -0,0 +1,32 @@ +/* Verify that unary operators that rvalue-convert a counted_by-annotated + pointer access do not ICE. The original PR123569 fix suppressed the + .ACCESS_WITH_SIZE wrapper creation for ++/-- (which keep an lvalue); + the rvalue-consuming ops (!, -, +) still receive the wrapper and must + strip it in build_unary_op. */ +/* { dg-do run } */ +/* { dg-options "-std=c99" } */ + +struct s { + int n; + char *p __attribute__((__counted_by__(n))); +}; + +int test_not (struct s *o) { return !o->p; } +long test_neg (struct s *o) { return -(long)o->p; } +long test_plus (struct s *o) { return +(long)o->p; } + +extern void abort (void); + +int main (void) { + char buf[4] = { 0 }; + struct s s = { .n = 4, .p = buf }; + if (test_not (&s) != 0) abort (); /* p is non-null */ + + struct s e = { .n = 0, .p = (void*)0 }; + if (test_not (&e) != 1) abort (); /* p is null */ + + /* test_neg / test_plus must just compile and run without ICE. */ + (void) test_neg (&s); + (void) test_plus (&s); + return 0; +} diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc index 6bce8c427543..0f96de200743 100644 --- a/gcc/c/c-typeck.cc +++ b/gcc/c/c-typeck.cc @@ -5779,6 +5779,18 @@ build_unary_op (location_t location, enum tree_code code, tree xarg, tree eptype = NULL_TREE; const char *invalid_op_diag; + /* If ARG is wrapped in a call to .ACCESS_WITH_SIZE (created when the + C parser rvalue-converts a counted_by-annotated member access, see + PR123569) unwrap it here. Unary operators that consume an rvalue + (!, -, +) read the value itself rather than dereferencing into the + pointed-to data, so the bounds-checking wrapper is unnecessary and + would otherwise reach build_unary_op while it is not equipped to + handle the wrapped form. PR123569 fixed the ++/-- side of this by + suppressing wrapper creation in the parser; the rvalue-consuming + ops still receive the wrapper and need to strip it here. */ + if (is_access_with_size_p (arg)) + xarg = arg = get_ref_from_access_with_size (arg); + gcc_checking_assert (!is_access_with_size_p (arg)); bool int_operands = EXPR_INT_CONST_OPERANDS (xarg); -- 2.34.1