Hi
I've come across an issue in readelf (binutils-2.2.7a), as follows:
Problem:
-------
"readelf -a input" crashes trying to access uninitialized memory (0) if given
the right input.
Reproduce:
---------
$ CFLAGS="-g -fsanitize=address" CC=clang ../configure --disable-shared
--disable-nls --disable-werror --disable-gdb --disable-libdecnumber
--disable-readline --disable-sim
$ ASAN_SYMBOLIZER_PATH=`which llvm-symbolizer` ./build/binutils/readelf -a input
==30209==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc
0x00000055c484 sp 0x7ffc692c6520 bp 0x7ffc692c6c50 T0)
#0 0x55c483 in dump_hppa_unwind
/path/binutils-2.2.7a.asan/build/binutils/../../binutils/readelf.c:7849
#1 0x553415 in hppa_process_unwind
/path/binutils-2.2.7a.asan/build/binutils/../../binutils/readelf.c:8129
#2 0x4b29f7 in process_unwind
/path/binutils-2.2.7a.asan/build/binutils/../../binutils/readelf.c:9262
#3 0x48c2d8 in process_object
/path/binutils-2.2.7a.asan/build/binutils/../../binutils/readelf.c:18751
#4 0x487870 in process_file
/path/binutils-2.2.7a.asan/build/binutils/../../binutils/readelf.c:19188
#5 0x485916 in main
/path/binutils-2.2.7a.asan/build/binutils/../../binutils/readelf.c:19247
#6 0x7f95f0d03f44 (/lib/x86_64-linux-gnu/libc.so.6+0x21f44)
#7 0x47e01c in _start
(/path/binutils-2.2.7a.asan/build/binutils/readelf+0x47e01c)
Details:
-------
in file readelf.c, function hppa_process_unwind():
if (! slurp_hppa_unwind_table (filedata, &aux, sec))
res = FALSE;
if (aux.table_len > 0)
{
if (! dump_hppa_unwind (filedata, &aux))
res = FALSE;
}
[...]
Even if the function slurp_hppa_unwind_table() fails, the function
dump_hppa_unwind()
is executed. In dump_hppa_unwind():
for (tp = aux->table; tp < aux->table + aux->table_len; ++tp)
{
bfd_vma offset;
const char * procname;
find_symbol_for_address (filedata, aux->funtab, aux->nfuns, aux->strtab,
aux->strtab_size, tp->start, &procname,
&offset);
[...]
Because slurp_hppa_unwind_table() failed, aux->table_len may be non-zero but
aux->table
is still 0. So tp is NULL and the program tries to access address 0x0.
I don't think this is exploitable because 0 is not controllable by user input:
it's the value
set in function hppa_process_unwind() thru:
memset (& aux, 0, sizeof (aux));
Fix:
----
Change:
if ( aux.table_len > 0)
to:
if ( res && aux.table_len > 0)
I can give you the input to trigger the bug if you'd like. I tried to attach it
to this email but could not as your server thinks there is malware in it...
Laurent
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