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From: Alex Coplan <acoplan@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r10-11189] varasm: Fix type confusion bug Date: Fri, 3 Feb 2023 18:35:07 +0000 (GMT) [thread overview] Message-ID: <20230203183507.7EC933858C2D@sourceware.org> (raw) https://gcc.gnu.org/g:f835376a1c6ebb2fe701dfbaf98739e1c805e86a commit r10-11189-gf835376a1c6ebb2fe701dfbaf98739e1c805e86a Author: Alex Coplan <alex.coplan@arm.com> Date: Thu Dec 1 17:36:02 2022 +0000 varasm: Fix type confusion bug This patch fixes a type confusion bug in varasm.c:assemble_variable. The problem is that the current code calls: sect = get_variable_section (decl, false); and then accesses sect->named.name without checking whether the section is in fact a named section. In the surrounding else clause, we only know that SECTION_STYLE (sect) != SECTION_NOSWITCH, so it is possible that the section is an unnamed section. In practice, this means that we end up doing a wild string compare between a function pointer and the string literal ".vtable_map_vars". This is because sect->named.name aliases sect->unnamed.callback in the section union. This can be seen in GDB with a simple testcase such as "int x;". This patch fixes the issue by checking the SECTION_STYLE of the section is in fact SECTION_NAMED before trying to do the string comparison. We drop the existing check of whether sect->named.name is non-NULL because this should presumably always be the case for a named section. gcc/ChangeLog: * varasm.c (assemble_variable): Fix type confusion bug when checking for ".vtable_map_vars" section. (cherry picked from commit de144fdab17dbbb64ccb540056ab78b4ffb3fbbc) Diff: --- gcc/varasm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/gcc/varasm.c b/gcc/varasm.c index d65985d9748..3ebcdc9aff8 100644 --- a/gcc/varasm.c +++ b/gcc/varasm.c @@ -2322,7 +2322,7 @@ assemble_variable (tree decl, int top_level ATTRIBUTE_UNUSED, else { /* Special-case handling of vtv comdat sections. */ - if (sect->named.name + if (SECTION_STYLE (sect) == SECTION_NAMED && (strcmp (sect->named.name, ".vtable_map_vars") == 0)) handle_vtv_comdat_section (sect, decl); else
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