From ff8577f64987a898e1dc5eb6afb66a404fb7bb16 Mon Sep 17 00:00:00 2001 From: Sergio Durigan Junior Date: Wed, 10 Jul 2019 16:18:27 -0400 Subject: [PATCH] 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 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 --- gdb/ChangeLog | 20 ++++++++++++++++++++ gdb/bsd-kvm.c | 7 +++---- gdb/corelow.c | 4 ++-- gdb/gdbsupport/pathstuff.c | 2 +- gdb/gdbsupport/pathstuff.h | 5 ++++- gdb/go32-nat.c | 3 ++- gdb/source.c | 3 +-- gdb/top.c | 18 ++++++++++++------ gdb/tracefile-tfile.c | 4 ++-- 9 files changed, 47 insertions(+), 19 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 7d4f982761..1a452be175 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,23 @@ +2019-12-14 Sergio Durigan Junior + + 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'. + 2019-12-13 Tom Tromey * contrib/ari/gdb_ari.sh: Remove check for multiple calls to diff --git a/gdb/bsd-kvm.c b/gdb/bsd-kvm.c index 21f978728d..895686ef62 100644 --- a/gdb/bsd-kvm.c +++ b/gdb/bsd-kvm.c @@ -114,14 +114,13 @@ bsd_kvm_target_open (const char *arg, int from_tty) if (arg) { - char *temp; - filename = tilde_expand (arg); if (filename[0] != '/') { - temp = concat (current_directory, "/", filename, (char *)NULL); + gdb::unique_xmalloc_ptr temp (gdb_abspath (filename)); + xfree (filename); - filename = temp; + filename = temp.release (); } } diff --git a/gdb/corelow.c b/gdb/corelow.c index bdbfae372d..6c1e47a555 100644 --- a/gdb/corelow.c +++ b/gdb/corelow.c @@ -44,6 +44,7 @@ #include "completer.h" #include "gdbsupport/filestuff.h" #include "build-id.h" +#include "gdbsupport/pathstuff.h" #ifndef O_LARGEFILE #define O_LARGEFILE 0 @@ -395,8 +396,7 @@ core_target_open (const char *arg, int from_tty) gdb::unique_xmalloc_ptr filename (tilde_expand (arg)); if (!IS_ABSOLUTE_PATH (filename.get ())) - filename.reset (concat (current_directory, "/", - filename.get (), (char *) NULL)); + filename = gdb_abspath (filename.get ()); flags = O_BINARY | O_LARGEFILE; if (write_files) diff --git a/gdb/gdbsupport/pathstuff.c b/gdb/gdbsupport/pathstuff.c index fafecd543d..aa51e8f36e 100644 --- a/gdb/gdbsupport/pathstuff.c +++ b/gdb/gdbsupport/pathstuff.c @@ -134,7 +134,7 @@ gdb_abspath (const char *path) if (path[0] == '~') return gdb_tilde_expand_up (path); - if (IS_ABSOLUTE_PATH (path)) + if (IS_ABSOLUTE_PATH (path) || current_directory == NULL) return make_unique_xstrdup (path); /* Beware the // my son, the Emacs barfs, the botch that catch... */ diff --git a/gdb/gdbsupport/pathstuff.h b/gdb/gdbsupport/pathstuff.h index 7d7c8cd028..e84685b654 100644 --- a/gdb/gdbsupport/pathstuff.h +++ b/gdb/gdbsupport/pathstuff.h @@ -44,7 +44,10 @@ extern gdb::unique_xmalloc_ptr Contrary to "gdb_realpath", this function uses CURRENT_DIRECTORY for the path expansion. This may lead to scenarios the current - working directory (CWD) is different than CURRENT_DIRECTORY. */ + working directory (CWD) is different than CURRENT_DIRECTORY. + + If CURRENT_DIRECTORY is NULL, this function returns a copy of + PATH. */ extern gdb::unique_xmalloc_ptr gdb_abspath (const char *path); diff --git a/gdb/go32-nat.c b/gdb/go32-nat.c index 8c71bd7650..94972a2f5c 100644 --- a/gdb/go32-nat.c +++ b/gdb/go32-nat.c @@ -507,7 +507,8 @@ go32_nat_target::wait (ptid_t ptid, struct target_waitstatus *status, } getcwd (child_cwd, sizeof (child_cwd)); /* in case it has changed */ - chdir (current_directory); + if (current_directory != NULL) + chdir (current_directory); if (a_tss.tss_irqn == 0x21) { diff --git a/gdb/source.c b/gdb/source.c index 2ec3fbe705..cf752a6938 100644 --- a/gdb/source.c +++ b/gdb/source.c @@ -540,8 +540,7 @@ add_path (const char *dirname, char **which_path, int parse_separators) new_name_holder.reset (concat (name, ".", (char *) NULL)); #endif else if (!IS_ABSOLUTE_PATH (name) && name[0] != '$') - new_name_holder.reset (concat (current_directory, SLASH_STRING, name, - (char *) NULL)); + new_name_holder = gdb_abspath (name); else new_name_holder.reset (savestring (name, p - name)); name = new_name_holder.get (); diff --git a/gdb/top.c b/gdb/top.c index e8ed3b2747..bc300e4754 100644 --- a/gdb/top.c +++ b/gdb/top.c @@ -54,6 +54,7 @@ #include "gdb_select.h" #include "gdbsupport/scope-exit.h" #include "gdbarch.h" +#include "gdbsupport/pathstuff.h" /* readline include files. */ #include "readline/readline.h" @@ -1994,12 +1995,13 @@ init_history (void) that was read. */ #ifdef __MSDOS__ /* No leading dots in file names are allowed on MSDOS. */ - history_filename = concat (current_directory, "/_gdb_history", - (char *)NULL); + const char *fname = "_gdb_history"; #else - history_filename = concat (current_directory, "/.gdb_history", - (char *)NULL); + const char *fname = ".gdb_history"; #endif + + gdb::unique_xmalloc_ptr temp (gdb_abspath (fname)); + history_filename = temp.release (); } read_history (history_filename); } @@ -2077,8 +2079,12 @@ set_history_filename (const char *args, directories the file written will be the same as the one that was read. */ if (!IS_ABSOLUTE_PATH (history_filename)) - history_filename = reconcat (history_filename, current_directory, "/", - history_filename, (char *) NULL); + { + gdb::unique_xmalloc_ptr temp (gdb_abspath (history_filename)); + + xfree (history_filename); + history_filename = temp.release (); + } } static void diff --git a/gdb/tracefile-tfile.c b/gdb/tracefile-tfile.c index 5c3837ec5b..0953b03781 100644 --- a/gdb/tracefile-tfile.c +++ b/gdb/tracefile-tfile.c @@ -32,6 +32,7 @@ #include "xml-tdesc.h" #include "target-descriptions.h" #include "gdbsupport/buffer.h" +#include "gdbsupport/pathstuff.h" #include #ifndef O_LARGEFILE @@ -470,8 +471,7 @@ tfile_target_open (const char *arg, int from_tty) gdb::unique_xmalloc_ptr filename (tilde_expand (arg)); if (!IS_ABSOLUTE_PATH (filename.get ())) - filename.reset (concat (current_directory, "/", filename.get (), - (char *) NULL)); + filename = gdb_abspath (filename.get ()); flags = O_BINARY | O_LARGEFILE; flags |= O_RDONLY; -- 2.34.1