coredump: Ensure proper size of sparse core files

If the last section of a core file ends with an unmapped or zero page,
the size of the file does not correspond with the last dump_skip() call.
gdb complains that the file is truncated and can be confusing to users.

After all of the vma sections are written, make sure that the file size
is no smaller than the current file position.

This problem can be demonstrated with gdb's bigcore testcase on the
sparc architecture.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 29a02daf08a97896c600e88317e646dbf3ab3c9b..422370293cfd8cfc9b0f527f73498ce7c28244be 100644 (file)
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -2298,6 +2298,7 @@ static int elf_core_dump(struct coredump_params *cprm)
                                goto end_coredump;
                }
        }
+       dump_truncate(cprm);
 
        if (!elf_core_write_extra_data(cprm))
                goto end_coredump;

diff --git a/fs/coredump.c b/fs/coredump.c
index e525b6017cdf863fd811425fb603070be40420b2..ae6b05629ca174d714bbdb3db477bee8f0d8bff8 100644 (file)
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -833,3 +833,21 @@ int dump_align(struct coredump_params *cprm, int align)
        return mod ? dump_skip(cprm, align - mod) : 1;
 }
 EXPORT_SYMBOL(dump_align);
+
+/*
+ * Ensures that file size is big enough to contain the current file
+ * postion. This prevents gdb from complaining about a truncated file
+ * if the last "write" to the file was dump_skip.
+ */
+void dump_truncate(struct coredump_params *cprm)
+{
+       struct file *file = cprm->file;
+       loff_t offset;
+
+       if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
+               offset = file->f_op->llseek(file, 0, SEEK_CUR);
+               if (i_size_read(file->f_mapping->host) < offset)
+                       do_truncate(file->f_path.dentry, offset, 0, file);
+       }
+}
+EXPORT_SYMBOL(dump_truncate);

diff --git a/include/linux/coredump.h b/include/linux/coredump.h
index d016a121a8c46492bd6feea5b093dcea9bf27933..28ffa94aed6b85d10531e7dc11864f9ebc8701f4 100644 (file)
--- a/include/linux/coredump.h
+++ b/include/linux/coredump.h
@@ -14,6 +14,7 @@ struct coredump_params;
 extern int dump_skip(struct coredump_params *cprm, size_t nr);
 extern int dump_emit(struct coredump_params *cprm, const void *addr, int nr);
 extern int dump_align(struct coredump_params *cprm, int align);
+extern void dump_truncate(struct coredump_params *cprm);
 #ifdef CONFIG_COREDUMP
 extern void do_coredump(const siginfo_t *siginfo);
 #else