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Avoid double-free with debuginfod

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PR gdb/29257 points out a possible double free when debuginfod is in
use.  Aside from some ugly warts in the symbol code (an ongoing
issue), the underlying issue in this particular case is that elfread.c
seems to assume that symfile_bfd_open will return NULL on error,
whereas in reality it throws an exception.  As this code isn't
prepared for an exception, bad things result.

This patch fixes the problem by introducing a non-throwing variant of
symfile_bfd_open and using it in the affected places.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29257
This commit is contained in:
Tom Tromey 2022-12-06 12:07:12 -07:00
parent 546c7898dc
commit f96328accd
3 changed files with 32 additions and 9 deletions
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19
gdb/elfread.c
View File

@ -1232,10 +1232,12 @@ elf_symfile_read_dwarf2 (struct objfile *objfile,
if (!debugfile.empty ())
{
gdb_bfd_ref_ptr debug_bfd (symfile_bfd_open (debugfile.c_str ()));
gdb_bfd_ref_ptr debug_bfd
(symfile_bfd_open_no_error (debugfile.c_str ()));
symbol_file_add_separate (debug_bfd, debugfile.c_str (),
symfile_flags, objfile);
if (debug_bfd != nullptr)
symbol_file_add_separate (debug_bfd, debugfile.c_str (),
symfile_flags, objfile);
}
else
{
@ -1255,13 +1257,12 @@ elf_symfile_read_dwarf2 (struct objfile *objfile,
if (fd.get () >= 0)
{
/* File successfully retrieved from server. */
gdb_bfd_ref_ptr debug_bfd (symfile_bfd_open (symfile_path.get ()));
gdb_bfd_ref_ptr debug_bfd
(symfile_bfd_open_no_error (symfile_path.get ()));
if (debug_bfd == nullptr)
warning (_("File \"%s\" from debuginfod cannot be opened as bfd"),
filename);
else if (build_id_verify (debug_bfd.get (), build_id->size,
build_id->data))
if (debug_bfd != nullptr
&& build_id_verify (debug_bfd.get (), build_id->size,
build_id->data))
{
symbol_file_add_separate (debug_bfd, symfile_path.get (),
symfile_flags, objfile);

17
gdb/symfile.c
View File

@ -1769,6 +1769,23 @@ symfile_bfd_open (const char *name)
return sym_bfd;
}
/* See symfile.h. */
gdb_bfd_ref_ptr
symfile_bfd_open_no_error (const char *name) noexcept
{
try
{
return symfile_bfd_open (name);
}
catch (const gdb_exception_error &err)
{
warning ("%s", err.what ());
}
return nullptr;
}
/* Return the section index for SECTION_NAME on OBJFILE. Return -1 if
the section was not found. */

5
gdb/symfile.h
View File

@ -276,6 +276,11 @@ extern void set_initial_language (void);
extern gdb_bfd_ref_ptr symfile_bfd_open (const char *);
/* Like symfile_bfd_open, but will not throw an exception on error.
Instead, it issues a warning and returns nullptr. */
extern gdb_bfd_ref_ptr symfile_bfd_open_no_error (const char *) noexcept;
extern int get_section_index (struct objfile *, const char *);
extern int print_symbol_loading_p (int from_tty, int mainline, int full);