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bfd_check_format_matches preserving matches vs. cleanups

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It didn't take long for oss-fuzz to find double frees due to a bug in
the cleanup logic.  It's seen when reading in any alpha-vms object
file except when alpha_vms_vec is the default.  But alpha_vms_vec is
of course the default when building for --target=alpha-dec-vms (and
naturally what I used to  test the cleanup support since that is the
only target with a cleanup that does anything currently).

Anyway, the bug is that if bfd_check_format_matches is to preserve a
match the cleanup for that match can't be run.  Quite obviously that
would destroy part of the match state.

	* format.c (struct bfd_preserve): Add cleanup field.
	(bfd_preserve_save): Add cleanup param and save.
	(bfd_preserve_restore): Return cleanup.
	(bfd_preserve_finish): Call the cleanup for the discarded match.
	(bfd_check_format_matches): Pass cleanup to bfd_preserve_save,
	and clear when preserving a match.  Restore cleanup too when
	restoring that match.
This commit is contained in:
Alan Modra 2020-03-03 20:27:36 +10:30
parent 478e490a4d
commit f57140990f
2 changed files with 29 additions and 5 deletions
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10
bfd/ChangeLog
View File

@ -1,3 +1,13 @@
2020-03-03 Alan Modra <amodra@gmail.com>
* format.c (struct bfd_preserve): Add cleanup field.
(bfd_preserve_save): Add cleanup param and save.
(bfd_preserve_restore): Return cleanup.
(bfd_preserve_finish): Call the cleanup for the discarded match.
(bfd_check_format_matches): Pass cleanup to bfd_preserve_save,
and clear when preserving a match. Restore cleanup too when
restoring that match.
2020-03-02 Alan Modra <amodra@gmail.com>
* cisco-core.c (cisco_core_file_p): Return bfd_cleanup.

24
bfd/format.c
View File

@ -106,6 +106,7 @@ struct bfd_preserve
unsigned int section_id;
struct bfd_hash_table section_htab;
const struct bfd_build_id *build_id;
bfd_cleanup cleanup;
};
/* When testing an object for compatibility with a particular target
@ -118,7 +119,8 @@ struct bfd_preserve
the subset. */
static bfd_boolean
bfd_preserve_save (bfd *abfd, struct bfd_preserve *preserve)
bfd_preserve_save (bfd *abfd, struct bfd_preserve *preserve,
bfd_cleanup cleanup)
{
preserve->tdata = abfd->tdata.any;
preserve->arch_info = abfd->arch_info;
@ -130,6 +132,7 @@ bfd_preserve_save (bfd *abfd, struct bfd_preserve *preserve)
preserve->section_htab = abfd->section_htab;
preserve->marker = bfd_alloc (abfd, 1);
preserve->build_id = abfd->build_id;
preserve->cleanup = cleanup;
if (preserve->marker == NULL)
return FALSE;
@ -153,7 +156,7 @@ bfd_reinit (bfd *abfd, unsigned int section_id, bfd_cleanup cleanup)
/* Restores bfd state saved by bfd_preserve_save. */
static void
static bfd_cleanup
bfd_preserve_restore (bfd *abfd, struct bfd_preserve *preserve)
{
bfd_hash_table_free (&abfd->section_htab);
@ -172,6 +175,7 @@ bfd_preserve_restore (bfd *abfd, struct bfd_preserve *preserve)
its arg, as well as its arg. */
bfd_release (abfd, preserve->marker);
preserve->marker = NULL;
return preserve->cleanup;
}
/* Called when the bfd state saved by bfd_preserve_save is no longer
@ -180,6 +184,15 @@ bfd_preserve_restore (bfd *abfd, struct bfd_preserve *preserve)
static void
bfd_preserve_finish (bfd *abfd ATTRIBUTE_UNUSED, struct bfd_preserve *preserve)
{
if (preserve->cleanup)
{
/* Run the cleanup, assuming that all it will need is the
tdata at the time the cleanup was returned. */
void *tdata = abfd->tdata.any;
abfd->tdata.any = preserve->tdata;
preserve->cleanup (abfd);
abfd->tdata.any = tdata;
}
/* It would be nice to be able to free more memory here, eg. old
tdata, but that's not possible since these blocks are sitting
inside bfd_alloc'd memory. The section hash is on a separate
@ -252,7 +265,7 @@ bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching)
save_targ = abfd->xvec;
preserve_match.marker = NULL;
if (!bfd_preserve_save (abfd, &preserve))
if (!bfd_preserve_save (abfd, &preserve, NULL))
goto err_ret;
/* If the target type was explicitly specified, just check that target. */
@ -381,8 +394,9 @@ bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching)
if (preserve_match.marker == NULL)
{
match_targ = abfd->xvec;
if (!bfd_preserve_save (abfd, &preserve_match))
if (!bfd_preserve_save (abfd, &preserve_match, cleanup))
goto err_ret;
cleanup = NULL;
}
}
}
@ -455,7 +469,7 @@ bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching)
whole bfd and restoring it would be even worse; the first thing
you notice is that the cached bfd file position gets out of sync. */
if (preserve_match.marker != NULL)
bfd_preserve_restore (abfd, &preserve_match);
cleanup = bfd_preserve_restore (abfd, &preserve_match);
if (match_count == 1)
{