From: Alex Coplan <alex.coplan@arm.com>
To: gcc-patches@gcc.gnu.org
Subject: [PATCH] varasm: Fix type confusion bug
Date: Thu, 1 Dec 2022 15:33:30 +0000 [thread overview]
Message-ID: <Y4jJSkO6Ccew5OjL@arm.com> (raw)
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Hi,
This patch fixes a type confusion bug in varasm.cc: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.
Bootstrapped/regtested on aarch64-none-linux-gnu, OK for trunk?
Thanks,
Alex
gcc/ChangeLog:
* varasm.cc (assemble_variable): Fix type confusion bug when
checking for ".vtable_map_vars" section.
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diff --git a/gcc/varasm.cc b/gcc/varasm.cc
index 9dfbebbb915..6851201b6a2 100644
--- a/gcc/varasm.cc
+++ b/gcc/varasm.cc
@@ -2400,7 +2400,7 @@ 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
next reply other threads:[~2022-12-01 15:33 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-01 15:33 Alex Coplan [this message]
2022-12-01 16:12 ` Richard Sandiford
2022-12-01 17:59 ` Alex Coplan
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