coredump: Ensure proper size of sparse core files

[ Upstream commit 4d22c75d4c7b5c5f4bd31054f09103ee490878fd ]

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>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 2472af2798c735d056d26775a17906db707aa9a7..cfd724f98332680abb17e2a916674c9593cd104a 100644 (file)
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -2296,6 +2296,7 @@ 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 eb9c92c9b20f5de5e325d7a05e5d055d0816989e..4407e27beca958048291ebf65c6ce22157b35271 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