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From: "jinoh.kang.kr at gmail dot com" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug backtrace/28721] New: Stack buffer overrun in i386_unwind_pc
Date: Fri, 24 Dec 2021 13:35:27 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D28721

            Bug ID: 28721
           Summary: Stack buffer overrun in i386_unwind_pc
           Product: gdb
           Version: HEAD
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: backtrace
          Assignee: unassigned at sourceware dot org
          Reporter: jinoh.kang.kr at gmail dot com
  Target Milestone: ---
             Flags: security?

Created attachment 13876
  --> https://sourceware.org/bugzilla/attachment.cgi?id=3D13876&action=3Ded=
it
Sample program that triggers crash

i386_unwind_pc calls frame_unwind_register with a 8-byte buffer, which can
overrun if a wider register (e.g. [XYZ]MM registers) is specified as the re=
turn
address register.

An example debugging session that reproduces the crash:

  $ gcc -o test gdb-unwind-pc-overrun.S   # from attachment
  $ gdb -q ./test
  Reading symbols from ./test...
  (No debugging symbols found in ./test)
  (gdb) start
  Temporary breakpoint 1 at 0x401106
  Starting program: /home/user/trxu/test=20

  Temporary breakpoint 1, 0x0000000000401106 in main ()
  (gdb) stepi   # (or bt)
  *** stack smashing detected ***: terminated
  Aborted (core dumped)

This bug should be trivial to fix: use frame_unwind_register_unsigned inste=
ad
(unless there are semantic differences between frame_unwind_register and
frame_unwind_register_unsigned that I missed).

--=20
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