linux-kernel - [RFC][PATCH 10/13] make dump_emit() use vfs_write() instead of banging at ->f

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Date:	Wed, 09 Oct 2013 01:15:47 +0100
From:	Al Viro <viro@....linux.org.uk>
To:	torvalds@...ux-foundation.org
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC][PATCH 10/13] make dump_emit() use vfs_write() instead of
 banging at ->f_op->write directly


... and deal with short writes properly - the output might be to pipe, after
all; as it is, e.g. no-MMU case of elf_fdpic coredump can write a whole lot
more than a page worth of data at one call.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/coredump.c |   17 ++++++++++++-----
 1 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index 319f973..478ebad 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -696,13 +696,20 @@ EXPORT_SYMBOL(dump_write);
 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
 {
 	struct file *file = cprm->file;
-	if (dump_interrupted() || !access_ok(VERIFY_READ, addr, nr))
-		return 0;
+	loff_t pos = file->f_pos;
+	ssize_t n;
 	if (cprm->written + nr > cprm->limit)
 		return 0;
-	if (file->f_op->write(file, addr, nr, &file->f_pos) != nr)
-		return 0;
-	cprm->written += nr;
+	while (nr) {
+		if (dump_interrupted())
+			return 0;
+		n = vfs_write(file, addr, nr, &pos);
+		if (n < 0)
+			return 0;
+		file->f_pos = pos;
+		cprm->written += n;
+		nr -= n;
+	}
 	return 1;
 }
 EXPORT_SYMBOL(dump_emit);
-- 
1.7.2.5


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