[binutils-gdb/binutils-2_40-branch] libctf: ctf-link outdated input check faulty

[binutils-gdb/binutils-2_40-branch] libctf: ctf-link outdated input check faulty

[Nick Alcock]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=999e7ed7a2bfd3a65468b383222d441a8071d8e4

commit 999e7ed7a2bfd3a65468b383222d441a8071d8e4
Author: Nick Alcock <nick.alcock@oracle.com>
Date:   Mon Jan 9 13:43:09 2023 +0000

    libctf: ctf-link outdated input check faulty
    
    This check has a pair of faults which, combined, can lead to memory
    corruption.  Firstly, it assumes that the values of the ctf_link_inputs
    hash are ctf_dict_t's: they are not, they are ctf_link_input_t's, a much
    shorter structure.  So the flags check which is the core of this is
    faulty (but happens, by chance, to give the right output on most
    architectures, since usually we happen to get a 0 here, so the test that
    checks this usually passes).  Worse, the warning that is emitted when
    the test fails is added to the wrong dict -- it's added to the input
    dict, whose warning list is never consumed, rendering the whole check
    useless.  But the dict it adds to is still the wrong type, so we end up
    overwriting something deep in memory (or, much more likely,
    dereferencing a garbage pointer and crashing).
    
    Fixing both reveals another problem: the link input is an *archive*
    consisting of multiple members, so we have to consider whether to check
    all of them for the outdated-func-info thing we are checking here.
    However, no compiler exists that emits a mixture of members with this
    flag on and members with it off, and the linker always reserializes (and
    upgrades) such things when it sees them: so all members in a given
    archive must have the same value of the flag, so we only need to check
    one member per input archive.
    
    libctf/
            PR libctf/29983
            * ctf-link.c (ctf_link_warn_outdated_inputs): Get the types of
            members of ctf_link_inputs right, fixing a possible spurious
            tesst failure / wild pointer deref / overwrite.  Emit the
            warning message into the right dict.

Diff:
---
 libctf/ctf-link.c | 35 +++++++++++++++++++++++++++++------
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/libctf/ctf-link.c b/libctf/ctf-link.c
index 2837168b2a6..016bce5f6d6 100644
--- a/libctf/ctf-link.c
+++ b/libctf/ctf-link.c
@@ -1848,19 +1848,42 @@ ctf_link_warn_outdated_inputs (ctf_dict_t *fp)
 {
   ctf_next_t *i = NULL;
   void *name_;
-  void *ifp_;
+  void *input_;
   int err;
 
-  while ((err = ctf_dynhash_next (fp->ctf_link_inputs, &i, &name_, &ifp_)) == 0)
+  while ((err = ctf_dynhash_next (fp->ctf_link_inputs, &i, &name_, &input_)) == 0)
     {
       const char *name = (const char *) name_;
-      ctf_dict_t *ifp = (ctf_dict_t *) ifp_;
+      ctf_link_input_t *input = (ctf_link_input_t *) input_;
+      ctf_next_t *j = NULL;
+      ctf_dict_t *ifp;
+      int err;
+
+      /* We only care about CTF archives by this point: lazy-opened archives
+	 have always been opened by this point, and short-circuited entries have
+	 a matching corresponding archive member. Entries with NULL clin_arc can
+	 exist, and constitute old entries renamed via a name changer: the
+	 renamed entries exist elsewhere in the list, so we can just skip
+	 those.  */
+
+      if (!input->clin_arc)
+	continue;
+
+      /* All entries in the archive will necessarily contain the same
+	 CTF_F_NEWFUNCINFO flag, so we only need to check the first. We don't
+	 even need to do that if we can't open it for any reason at all: the
+	 link will fail later on regardless, since an input can't be opened. */
+
+      ifp = ctf_archive_next (input->clin_arc, &j, NULL, 0, &err);
+      if (!ifp)
+	continue;
+      ctf_next_destroy (j);
 
       if (!(ifp->ctf_header->cth_flags & CTF_F_NEWFUNCINFO)
 	  && (ifp->ctf_header->cth_varoff - ifp->ctf_header->cth_funcoff) > 0)
-	ctf_err_warn (ifp, 1, 0, _("linker input %s has CTF func info but uses "
-				   "an old, unreleased func info format: "
-				   "this func info section will be dropped."),
+	ctf_err_warn (fp, 1, 0, _("linker input %s has CTF func info but uses "
+				  "an old, unreleased func info format: "
+				  "this func info section will be dropped."),
 		      name);
     }
   if (err != ECTF_NEXT_END)