Fix segfault if target_fileio_read_alloc fails

Check for target_fileio_read_alloc failure in linux_fill_prpsinfo
before dereferencing buffer. This fixes a segfault in the 'gcore'
command when attached to certain remote targets.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=32441
Approved-By: Andrew Burgess <aburgess@redhat.com>

diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c
index d3ab02d03e025ac7a41d3be427caf3d3d181b6ed..735d20dc05011e558d46819108e41a251a8ee154 100644 (file)
--- a/gdb/linux-tdep.c
+++ b/gdb/linux-tdep.c
@@ -854,7 +854,7 @@ linux_info_proc (struct gdbarch *gdbarch, const char *args,
     {
       xsnprintf (filename, sizeof filename, "/proc/%ld/cmdline", pid);
       gdb_byte *buffer;
-      ssize_t len = target_fileio_read_alloc (NULL, filename, &buffer);
+      LONGEST len = target_fileio_read_alloc (nullptr, filename, &buffer);
 
       if (len > 0)
        {
@@ -2180,17 +2180,17 @@ linux_fill_prpsinfo (struct elf_internal_linux_prpsinfo *p)
   /* The number of fields read by `sscanf'.  */
   int n_fields = 0;
 
-  gdb_assert (p != NULL);
+  gdb_assert (p != nullptr);
 
   /* Obtaining PID and filename.  */
   pid = inferior_ptid.pid ();
   xsnprintf (filename, sizeof (filename), "/proc/%d/cmdline", (int) pid);
   /* The full name of the program which generated the corefile.  */
-  gdb_byte *buf = NULL;
-  size_t buf_len = target_fileio_read_alloc (NULL, filename, &buf);
+  gdb_byte *buf = nullptr;
+  LONGEST buf_len = target_fileio_read_alloc (nullptr, filename, &buf);
   gdb::unique_xmalloc_ptr<char> fname ((char *)buf);
 
-  if (buf_len < 1 || fname.get ()[0] == '\0')
+  if (buf_len < 1 || fname.get () == nullptr || fname.get ()[0] == '\0')
     {
       /* No program name was read, so we won't be able to retrieve more
         information about the process.  */