From 44e4c7757a733949d511d97a7d95db913f423f1b Mon Sep 17 00:00:00 2001 From: Andrew Burgess Date: Fri, 6 Dec 2019 23:12:29 +0000 Subject: gdb: Handle malformed ELF, symbols in non-allocatable sections I ended up debugging a malformed ELF where a section containing executable code was not correctly marked as allocatable. Before realising the ELF was corrupted I tried to place a breakpoint on a symbol in the non-allocatable, executable section, and GDB crashed. Though trying to debug such an ELF clearly isn't going to go well I would prefer, as far as possible, that any input, no matter how corrupted, not crash GDB. The crash occurs when trying to set a breakpoint on the name of a function from the corrupted section. GDB converts the symbol to a symtab_and_line, and looks up a suitable section for this. The problem is that the section is actually an obj_section, which is stored in the table within the objfile, and we only initialise this table for allocatable sections (see add_to_objfile_sections_full in objfiles.c). So, if the symbol is in a non-allocatable section then we end up referencing an uninitialised obj_section. Later we call get_sal_arch on the symtab_and_line, which calls get_objfile_arch, which uses the objfile from the uninitialised obj_section, which will be nullptr, at which point GDB crashes. The fix I propose here is that when we setup the section references on msymbols, we should check if the bfd_section being referenced is allocatable or not. If it is not then we should set the section reference back to the default 0 section (see how MSYMBOL_OBJ_SECTION and SYMBOL_OBJ_SECTION treat the 0 section index). With this fix in place GDB no longer crashes. Instead GDB creates the breakpoint at the non-allocated address, and then fails, with an error, when it tries to insert the breakpoint. gdb/ChangeLog: * elfread.c (record_minimal_symbol): Set section index to 0 for non-allocatable sections. gdb/testsuite/ChangeLog: * gdb.dwarf2/dw2-bad-elf-other.S: New file. * gdb.dwarf2/dw2-bad-elf.c: New file. * gdb.dwarf2/dw2-bad-elf.exp: New file. Change-Id: Ie05436ab4c6a71440304d20ee639dfb021223f8b --- gdb/ChangeLog | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'gdb/ChangeLog') diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 7a1c81d..fc4920e 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2020-01-13 Andrew Burgess + + * elfread.c (record_minimal_symbol): Set section index to 0 for + non-allocatable sections. + 2020-01-13 Ali Tamur -- cgit v1.1