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* [gcc r10-11189] varasm: Fix type confusion bug
@ 2023-02-03 18:35 Alex Coplan
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From: Alex Coplan @ 2023-02-03 18:35 UTC (permalink / raw)
To: gcc-cvs
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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