[PATCH 1/3] coredump: introduce dump_interrupted()

Oleg Nesterov
2013-03-08T18:01:09Z

By discussion with Mandeep Singh Baines <msb@chromium.org>.

Change dump_write(), dump_seek() and do_coredump() to check
signal_pending() and abort if it is true.

We add the new trivial helper, dump_interrupted(), to document that
this probably needs more work and to simplify the potential freezer
changes. Perhaps it will have more callers.

Ideally it should do try_to_freeze() but then we need the unpleasant
changes in dump_write() and wait_for_dump_helpers(). So far we simply
accept the fact that the freezer can truncate a core-dump but at least
you can reliably suspend.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
fs/coredump.c | 20 +++++++++++++++++---
1 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index 5503d94..66f65f0 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -418,6 +418,17 @@ static void coredump_finish(struct mm_struct *mm, bool core_dumped)
mm->core_state = NULL;
}

+static bool dump_interrupted(void)
+{
+ /*
+ * SIGKILL or freezing() interrupt the coredumping. Perhaps we
+ * can do try_to_freeze() and check __fatal_signal_pending(),
+ * but then we need to teach dump_write() to restart and clear
+ * TIF_SIGPENDING.
+ */
+ return signal_pending(current);
+}
+
static void wait_for_dump_helpers(struct file *file)
{
struct pipe_inode_info *pipe;
@@ -636,7 +647,7 @@ void do_coredump(siginfo_t *siginfo)
if (displaced)
put_files_struct(displaced);

- core_dumped = binfmt->core_dump(&cprm);
+ core_dumped = !dump_interrupted() && binfmt->core_dump(&cprm);

if (ispipe && core_pipe_limit)
wait_for_dump_helpers(cprm.file);
@@ -664,7 +675,9 @@ fail:
*/
int dump_write(struct file *file, const void *addr, int nr)
{
- return access_ok(VERIFY_READ, addr, nr) && file->f_op->write(file, addr, nr, &file->f_pos) == nr;
+ return !dump_interrupted() &&
+ access_ok(VERIFY_READ, addr, nr) &&
+ file->f_op->write(file, addr, nr, &file->f_pos) == nr;
}
EXPORT_SYMBOL(dump_write);

@@ -673,7 +686,8 @@ int dump_seek(struct file *file, loff_t off)
int ret = 1;

if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
- if (file->f_op->llseek(file, off, SEEK_CUR) < 0)
+ if (dump_interrupted() ||
+ file->f_op->llseek(file, off, SEEK_CUR) < 0)
return 0;
} else {
char *buf = (char *)get_zeroed_page(GFP_KERNEL);
--
1.5.5.1