From 723adb650a31859d7cc45832cb8adca0206455ed Mon Sep 17 00:00:00 2001 From: Sandra Loosemore Date: Thu, 25 Apr 2019 07:27:02 -0700 Subject: [PATCH] Detect invalid length field in debug frame FDE header. GDB was failing to catch cases where a corrupt ELF or core file contained an invalid length value in a Dwarf debug frame FDE header. It was checking for buffer overflow but not cases where the length was negative or caused pointer wrap-around. In addition to the additional validity check, this patch cleans up the multiple signed/unsigned conversions on the length field so that an unsigned representation is used consistently throughout. This patch fixes CVE-2017-9778 and PR gdb/21600. 2019-04-25 Sandra Loosemore Kang Li PR gdb/21600 * dwarf2-frame.c (read_initial_length): Be consistent about using unsigned representation of length. (decode_frame_entry_1): Likewise. Check for wraparound of end pointer as well as buffer overflow. --- gdb/ChangeLog | 10 ++++++++++ gdb/dwarf2-frame.c | 14 +++++++------- 2 files changed, 17 insertions(+), 7 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 21358ff3118..476dd19f7ce 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,13 @@ +2019-04-25 Sandra Loosemore + Kang Li + + PR gdb/21600 + + * dwarf2-frame.c (read_initial_length): Be consistent about using + unsigned representation of length. + (decode_frame_entry_1): Likewise. Check for wraparound of + end pointer as well as buffer overflow. + 2019-04-24 Sergio Durigan Junior * aarch64-tdep.c (aarch64_gdbarch_init): Use "pulongest" to print diff --git a/gdb/dwarf2-frame.c b/gdb/dwarf2-frame.c index e2bf61bd309..b697afa5a13 100644 --- a/gdb/dwarf2-frame.c +++ b/gdb/dwarf2-frame.c @@ -1487,7 +1487,7 @@ static ULONGEST read_initial_length (bfd *abfd, const gdb_byte *buf, unsigned int *bytes_read_ptr) { - LONGEST result; + ULONGEST result; result = bfd_get_32 (abfd, buf); if (result == 0xffffffff) @@ -1788,7 +1788,7 @@ decode_frame_entry_1 (struct comp_unit *unit, const gdb_byte *start, { struct gdbarch *gdbarch = get_objfile_arch (unit->objfile); const gdb_byte *buf, *end; - LONGEST length; + ULONGEST length; unsigned int bytes_read; int dwarf64_p; ULONGEST cie_id; @@ -1799,15 +1799,15 @@ decode_frame_entry_1 (struct comp_unit *unit, const gdb_byte *start, buf = start; length = read_initial_length (unit->abfd, buf, &bytes_read); buf += bytes_read; - end = buf + length; - - /* Are we still within the section? */ - if (end > unit->dwarf_frame_buffer + unit->dwarf_frame_size) - return NULL; + end = buf + (size_t) length; if (length == 0) return end; + /* Are we still within the section? */ + if (end <= buf || end > unit->dwarf_frame_buffer + unit->dwarf_frame_size) + return NULL; + /* Distinguish between 32 and 64-bit encoded frame info. */ dwarf64_p = (bytes_read == 12); -- 2.30.2