From f57140990f9be3232ffbc708fb1aade032052c80 Mon Sep 17 00:00:00 2001 From: Alan Modra Date: Tue, 3 Mar 2020 20:27:36 +1030 Subject: [PATCH] bfd_check_format_matches preserving matches vs. cleanups 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. --- bfd/ChangeLog | 10 ++++++++++ bfd/format.c | 24 +++++++++++++++++++----- 2 files changed, 29 insertions(+), 5 deletions(-) diff --git a/bfd/ChangeLog b/bfd/ChangeLog index 1f9e20581f..ff2881f966 100644 --- a/bfd/ChangeLog +++ b/bfd/ChangeLog @@ -1,3 +1,13 @@ +2020-03-03 Alan Modra + + * 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 * cisco-core.c (cisco_core_file_p): Return bfd_cleanup. diff --git a/bfd/format.c b/bfd/format.c index b181742f3b..61f26c6042 100644 --- a/bfd/format.c +++ b/bfd/format.c @@ -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) {