[PATCH] lguest example launcher truncates block device file to 0length on problems

From: Rusty Russell
Date: Wed Sep 26 2007 - 01:16:40 EST

From: Chris Malley <mail@xxxxxxxxxxxxxxxxx>

The function should also use ftruncate64() rather than ftruncate() to prevent
files over 4GB (not uncommon for a root filesystem) being zeroed.

Signed-off-by: Chris Malley <mail@xxxxxxxxxxxxxxxxx>
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>

diff -r bcbb99849fd9 Documentation/lguest/lguest.c
--- a/Documentation/lguest/lguest.c Wed Sep 26 12:21:40 2007 +1000
+++ b/Documentation/lguest/lguest.c Wed Sep 26 14:15:38 2007 +1000
@@ -882,7 +882,7 @@ static u32 handle_block_output(int fd, c
* of the block file (possibly extending it). */
if (off + len > device_len) {
/* Trim it back to the correct length */
- ftruncate(dev->fd, device_len);
+ ftruncate64(dev->fd, device_len);
/* Die, bad Guest, die. */
errx(1, "Write past end %llu+%u", off, len);

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