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Sergio Durigan Junior ff8577f649 Guard against 'current_directory == NULL' on gdb_abspath (PR gdb/23613)
Ref.: https://bugzilla.redhat.com/show_bug.cgi?id=1728147
Ref.: https://sourceware.org/bugzilla/show_bug.cgi?id=23613

Hi,

This bug has been reported against Fedora GDB, but there's also an
upstream bug.  The problem reported is that GDB segfaults when the
working directory is deleted.  It's pretty use to reproduce it:

  mkdir bla
  cd bla
  rmdir ../bla
  gdb echo

Debugging the problem is a bit tricky, because, since the current
directory doesn't exist anymore, a corefile cannot be saved there.
After a few attempts, I came up with the following:

  gdb -ex 'shell mkdir bla' -ex 'cd bla' -ex 'shell rmdir ../bla' -ex 'r echo' ./gdb/gdb

This assumes that you're inside a build directory which contains
./gdb/gdb, of course.

After investigating it, I found that the problem happens at
gdb_abspath, where we're dereferencing 'current_directory' without
checking if it's NULL:

    ...
    (concat (current_directory,
	     IS_DIR_SEPARATOR (current_directory[strlen (current_directory) - 1])
	     ? "" : SLASH_STRING,
    ...

So I fixed the problem with the patch below.  The idea is that, if
'current_directory' is NULL, then the final string returned should be
just the "path".

After fixing the bug, I found a similar one reported against our
bugzilla: PR gdb/23613.  The problem is the same, but the reproducer
is a bit different.

I really tried writing a testcase for this, but unfortunately it's
apparently not possible to start GDB inside a non-existent directory
with DejaGNU.

I regression tested this patch on the BuildBot, and no regressions
were found.

gdb/ChangeLog:
2019-12-14  Sergio Durigan Junior  <sergiodj@redhat.com>

	https://bugzilla.redhat.com/show_bug.cgi?id=1728147
	PR gdb/23613
	* bsd-kvm.c (bsd_kvm_target_open): Use 'gdb_abspath'.
	* corelow.c: Include 'gdbsupport/pathstuff.h'.
	(core_target_open): Use 'gdb_abspath'.
	* gdbsupport/pathstuff.c (gdb_abspath): Guard against
	'current_directory == NULL' case.
	* gdbsupport/pathstuff.h (gdb_abspath): Expand comment and
	explain what happens when 'current_directory' is NULL.
	* go32-nat.c (go32_nat_target::wait): Check if
	'current_directory' is NULL before call to 'chdir'.
	* source.c (add_path): Use 'gdb_abspath'.
	* top.c: Include 'gdbsupport/pathstuff.h'.
	(init_history): Use 'gdb_abspath'.
	(set_history_filename): Likewise.
	* tracefile-tfile.c: Include 'gdbsupport/pathstuff.h'.
	(tfile_target_open): Use 'gdb_abspath'.

Change-Id: Ibb0932fa25bc5c2d3ae4a7f64bd7f32885ca403b
2019-12-13 23:49:29 -05:00
bfd Automatic date update in version.in 2019-12-14 00:00:16 +00:00
binutils Make bfd_get_8 return a bfd_vma like other bfd_get_* functions 2019-12-11 21:14:19 +10:30
config
contrib
cpu Remove more shifts for sign/zero extension 2019-12-11 21:14:19 +10:30
elfcpp
etc
gas i386: Also check R12-R15 registers when optimizing testq to testb 2019-12-12 12:31:26 -08:00
gdb Guard against 'current_directory == NULL' on gdb_abspath (PR gdb/23613) 2019-12-13 23:49:29 -05:00
gnulib
gold
gprof
include Fix unused function error 2019-12-12 09:12:02 -03:00
intl
ld i386: Add tests for -malign-branch-boundary and -malign-branch 2019-12-12 12:03:45 -08:00
libctf
libdecnumber
libiberty
opcodes csky: tidy csky_chars_to_number 2019-12-12 16:46:45 +10:30
readline
sim [ARM, sim] Fix build error and warnings 2019-12-06 18:16:20 -03:00
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		   README for GNU development tools

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