Bug 16817 - gdb crashes with mangled symbol name
Summary: gdb crashes with mangled symbol name
Alias: None
Product: gdb
Classification: Unclassified
Component: backtrace (show other bugs)
Version: 7.6
: P2 normal
Target Milestone: ---
Assignee: Gary Benson
Depends on:
Reported: 2014-04-07 17:21 UTC by Tavis Ormandy
Modified: 2014-05-14 14:35 UTC (History)
2 users (show)

See Also:
Last reconfirmed:

Patch, free resources after call to gnu_special. (880 bytes, patch)
2014-05-09 14:37 UTC, Andrew Burgess
Details | Diff

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Description Tavis Ormandy 2014-04-07 17:21:11 UTC
I have a library with a mangled symbol called _QueueNotification_QueueController__$4PPPPPPPM_A_INotice___Z that causes gdb to crash in libiberty. This can be reproduced like this:

$ printf '.set _QueueNotification_QueueController__$4PPPPPPPM_A_INotice___Z, 0xDEADBEEF\n' | as --32 -gstabs+
$ gdb -q -ex 'add-symbol-file a.out 0'
add symbol table from file "a.out" at
	.text_addr = 0x0
Reading symbols from a.out...Segmentation fault (core dumped)

$ gdb -q --args gdb -q -ex 'add-symbol-file a.out 0'
Reading symbols from /usr/bin/gdb...Reading symbols from /usr/lib/debug/usr/bin/gdb.debug...done.
(gdb) r
Starting program: /usr/bin/gdb -q -ex add-symbol-file\ a.out\ 0
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
Detaching after fork from child process 32347.
add symbol table from file "a.out" at
	.text_addr = 0x0
Program received signal SIGSEGV, Segmentation fault.
strlen () at ../sysdeps/x86_64/strlen.S:106
106		movdqu	(%rax), %xmm12
Missing separate debuginfos, use: debuginfo-install pcre-8.33-4.fc20.x86_64
(gdb) bt
#0  strlen () at ../sysdeps/x86_64/strlen.S:106
#1  0x000000000075abc5 in work_stuff_copy_to_from (to=to@entry=0x7fffffffd5f0, from=from@entry=0x7fffffffd740) at ../../libiberty/cplus-dem.c:1269
#2  0x000000000075fa39 in iterate_demangle_function (work=work@entry=0x7fffffffd740, mangled=mangled@entry=0x7fffffffd6c8, declp=declp@entry=0x7fffffffd6e0, scan=0xe4c4db "__$4PPPPPPPM_A_INotice___Z")
    at ../../libiberty/cplus-dem.c:2640
#3  0x00000000007605f9 in demangle_prefix (declp=0x7fffffffd6e0, mangled=0x7fffffffd6c8, work=0x7fffffffd740) at ../../libiberty/cplus-dem.c:2880
#4  internal_cplus_demangle (work=work@entry=0x7fffffffd740, mangled=0xe4c4ba "QueueNotification_QueueController__$4PPPPPPPM_A_INotice___Z", 
    mangled@entry=0xe4c4b9 "_QueueNotification_QueueController__$4PPPPPPPM_A_INotice___Z") at ../../libiberty/cplus-dem.c:1181
#5  0x000000000075b56d in cplus_demangle (mangled=mangled@entry=0xe4c4b9 "_QueueNotification_QueueController__$4PPPPPPPM_A_INotice___Z", options=options@entry=3) at ../../libiberty/cplus-dem.c:873
#6  0x00000000006c25eb in bfd_demangle (abfd=abfd@entry=0x0, name=name@entry=0xe4c4b9 "_QueueNotification_QueueController__$4PPPPPPPM_A_INotice___Z", options=options@entry=3) at ../../bfd/bfd.c:1875
#7  0x0000000000685e2c in gdb_demangle (name=name@entry=0xe4c4b9 "_QueueNotification_QueueController__$4PPPPPPPM_A_INotice___Z", options=options@entry=3) at ../../gdb/cp-support.c:1484
#8  0x000000000057deaf in symbol_find_demangled_name (mangled=0xe4c4b9 "_QueueNotification_QueueController__$4PPPPPPPM_A_INotice___Z", gsymbol=0xe5be28) at ../../gdb/symtab.c:600
#9  symbol_set_names (gsymbol=gsymbol@entry=0xe5be28, linkage_name=linkage_name@entry=0xe4c4b9 "_QueueNotification_QueueController__$4PPPPPPPM_A_INotice___Z", len=len@entry=60, copy_name=copy_name@entry=0, 
    objfile=objfile@entry=0xe53d00) at ../../gdb/symtab.c:773
#10 0x00000000005ea9c5 in prim_record_minimal_symbol_full (name=<optimized out>, name@entry=0x800000000 <Address 0x800000000 out of bounds>, name_len=60, copy_name=copy_name@entry=0, address=3735928559, 
    ms_type=ms_type@entry=mst_abs, section=<optimized out>, objfile=0xe53d00) at ../../gdb/minsyms.c:942
#11 0x0000000000513764 in record_minimal_symbol (name=0x800000000 <Address 0x800000000 out of bounds>, name@entry=0xe4c4b9 "_QueueNotification_QueueController__$4PPPPPPPM_A_INotice___Z", 
    name_len=<optimized out>, copy_name=copy_name@entry=0, address=<optimized out>, address@entry=3735928559, ms_type=ms_type@entry=mst_abs, bfd_section=<optimized out>, objfile=objfile@entry=0xe53d00)
    at ../../gdb/elfread.c:216
#12 0x0000000000513ceb in elf_symtab_read (objfile=objfile@entry=0xe53d00, type=type@entry=0, number_of_symbols=number_of_symbols@entry=6, symbol_table=symbol_table@entry=0xdeee30, copy_names=copy_names@entry=0)
    at ../../gdb/elfread.c:564
#13 0x0000000000515b65 in elf_symfile_read (objfile=0xe53d00, symfile_flags=2) at ../../gdb/elfread.c:2339
#14 0x0000000000589a19 in read_symbols (objfile=objfile@entry=0xe53d00, add_flags=add_flags@entry=2) at ../../gdb/symfile.c:831
#15 0x00000000005895b2 in syms_from_objfile_1 (add_flags=2, addrs=0xdfac20, objfile=0xe53d00) at ../../gdb/symfile.c:999
#16 syms_from_objfile (add_flags=2, addrs=0x1, objfile=0xe53d00) at ../../gdb/symfile.c:1015
#17 symbol_file_add_with_addrs (abfd=abfd@entry=0xe00590, add_flags=add_flags@entry=2, addrs=addrs@entry=0xdfac20, flags=flags@entry=8, parent=parent@entry=0x0) at ../../gdb/symfile.c:1110
#18 0x0000000000589ae8 in symbol_file_add_from_bfd (parent=0x0, flags=8, addrs=0xdfac20, add_flags=2, abfd=0xe00590) at ../../gdb/symfile.c:1197
#19 symbol_file_add (name=name@entry=0xc49050 "a.out", add_flags=2, addrs=addrs@entry=0xdfac20, flags=flags@entry=8) at ../../gdb/symfile.c:1211
#20 0x0000000000589e6c in add_symbol_file_command (args=<optimized out>, from_tty=1) at ../../gdb/symfile.c:2320
#21 0x00000000006724cf in execute_command (p=<optimized out>, p@entry=0x7fffffffe220 "add-symbol-file a.out 0", from_tty=from_tty@entry=1) at ../../gdb/top.c:482
#22 0x00000000005b05be in catch_command_errors (command=0x6722a0 <execute_command>, arg=0x7fffffffe220 "add-symbol-file a.out 0", from_tty=1, mask=mask@entry=6) at ../../gdb/exceptions.c:551
#23 0x00000000005b2ffa in captured_main (data=data@entry=0x7fffffffdd90) at ../../gdb/main.c:1114
#24 0x00000000005b04ca in catch_errors (func=func@entry=0x5b27e0 <captured_main>, func_args=func_args@entry=0x7fffffffdd90, errstring=errstring@entry=0x78ecb3 "", mask=mask@entry=6) at ../../gdb/exceptions.c:524
#25 0x00000000005b3c54 in gdb_main (args=args@entry=0x7fffffffdd90) at ../../gdb/main.c:1160
#26 0x0000000000457d1e in main (argc=<optimized out>, argv=<optimized out>) at ../../gdb/gdb.c:34
(gdb) frame 1
#1  0x000000000075abc5 in work_stuff_copy_to_from (to=to@entry=0x7fffffffd5f0, from=from@entry=0x7fffffffd740) at ../../libiberty/cplus-dem.c:1269
1269	      int len = strlen (from->btypevec[i]) + 1;
(gdb) p/x *from
$1 = {options = 0x103, typevec = 0x0, ktypevec = 0x0, btypevec = 0xd741e0, numk = 0x0, numb = 0x1, ksize = 0x0, bsize = 0x5, ntypes = 0x0, typevec_size = 0x0, constructor = 0x0, destructor = 0x0, 
  static_type = 0x0, temp_start = 0x0, type_quals = 0x0, dllimported = 0x0, tmpl_argvec = 0x0, ntmpl_args = 0x0, forgetting_types = 0x0, previous_argument = 0x0, nrepeats = 0x0}
(gdb) p/x from->btypevec
$2 = 0xd741e0
(gdb) p/x from->btypevec[i]
$3 = 0x0
(gdb) p/x i
$4 = 0x0
Comment 1 Gary Benson 2014-04-08 14:32:47 UTC
(gdb) set lang c++
(gdb) maint demangle _QueueNotification_QueueController__$4PPPPPPPM_A_INotice___ZSegmentation fault (core dumped)

Ok, I see this too.
Comment 2 Gary Benson 2014-04-08 14:48:54 UTC
What language/compiler is this please?  I don't recognise the mangling style.
Comment 3 Tavis Ormandy 2014-04-08 18:20:16 UTC
I don't know, if I had to guess I would say some form of delphi (I don't have the source code).

I don't expect gdb to be able to demangle this nonsense, just not crash so I can get a backtrace :-)
Comment 4 Gary Benson 2014-04-10 11:54:38 UTC
I started a thread about not crashing here:
Comment 5 Gary Benson 2014-05-09 10:11:40 UTC
Patch series submitted:
Comment 6 Andrew Burgess 2014-05-09 14:37:41 UTC
Created attachment 7594 [details]
Patch, free resources after call to gnu_special.

Patch posted upstream, fixes specific crash in this case:
Comment 7 Gary Benson 2014-05-09 14:51:13 UTC
Yeah, I should have been more specific, the patch series I posted was a fix for the generic case that the demangler crashing takes GDB with it.
Comment 8 Gary Benson 2014-05-14 14:35:17 UTC
The specific case of the above mentioned symbol crashing GDB has been fixed with this GCC commit:

I've filed the generic case that GDB cannot cope with demangler segfaults as bug 16944.