[PATCH] initramfs: Fix initramfs to work with hardlinked init

[PATCH] initramfs: Fix initramfs to work with hardlinked init

[Randy Robertson]

Change cb6ff208076b5f434db1b8c983429269d719cef5 seems to have broken
booting from initramfs with /sbin/init being a hardlink.  It seems like
the logic required for XIP on nommu, i.e. ftruncate to reported cpio
header file size (body_len) is broken for hardlinks, which have
a reported size of 0, and the truncate thus nukes the contents of the
file (in my case busybox), making boot impossible and ending with runaway
loop modprobe binfmt-0000 - and of course 0000 is not a valid binary format.

My fix is to only call ftruncate if size is non-zero which fixes things
for me, but I'm not certain whether this will break XIP for those files
on nommu systems, although I would guess not.

This update adds David's ack and fixes whitespace.

Signed-off-by: Randy Robertson <rmrobert@vmware.com>
Acked-by: David Howells <dhowells@redhat.com>
---
 init/initramfs.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/init/initramfs.c b/init/initramfs.c
index 80cd713..ddf30d1 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -310,7 +310,8 @@ static int __init do_name(void)
 			if (wfd >= 0) {
 				sys_fchown(wfd, uid, gid);
 				sys_fchmod(wfd, mode);
-				sys_ftruncate(wfd, body_len);
+				if (body_len)
+					sys_ftruncate(wfd, body_len);
 				vcollected = kstrdup(collected, GFP_KERNEL);
 				state = CopyFile;
 			}

Re: [PATCH] initramfs: Fix initramfs to work with hardlinked init

[H. Peter Anvin]

Randy Robertson wrote:
> Change cb6ff208076b5f434db1b8c983429269d719cef5 seems to have broken
> booting from initramfs with /sbin/init being a hardlink.  It seems like
> the logic required for XIP on nommu, i.e. ftruncate to reported cpio
> header file size (body_len) is broken for hardlinks, which have
> a reported size of 0, and the truncate thus nukes the contents of the
> file (in my case busybox), making boot impossible and ending with runaway
> loop modprobe binfmt-0000 - and of course 0000 is not a valid binary format.
> 
> My fix is to only call ftruncate if size is non-zero which fixes things
> for me, but I'm not certain whether this will break XIP for those files
> on nommu systems, although I would guess not.
> 
> This update adds David's ack and fixes whitespace.
> 
> Signed-off-by: Randy Robertson <rmrobert@vmware.com>
> Acked-by: David Howells <dhowells@redhat.com>

Looks right to me.

Acked-by: H. Peter Anvin <hpa@zytor.com>

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

[PATCH] initramfs: Fix initramfs to work with hardlinked init.

[Randy Robertson]

Change cb6ff208076b5f434db1b8c983429269d719cef5 seems to have broken
booting from initramfs with /sbin/init being a hardlink.  It seems like
the logic required for XIP on nommu, i.e. ftruncate to reported cpio
header file size (body_len) is broken for hardlinks, which have
a reported size of 0, and the truncate thus nukes the contents of the
file (in my case busybox), making boot impossible and ending with runaway
loop modprobe binfmt-0000 - and of course 0000 is not a valid binary format.

My fix is to only call ftruncate if size is non-zero which fixes things
for me, but I'm not certain whether this will break XIP for those files
on nommu systems, although I would guess not.

Signed-off-by: Randy Robertson <rmrobert@vmware.com>
---
diff --git a/init/initramfs.c b/init/initramfs.c
index d9c941c..4675f62 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -317,7 +317,8 @@ static int __init do_name(void)
			if (wfd >= 0) {
				sys_fchown(wfd, uid, gid);
				sys_fchmod(wfd, mode);
-			       sys_ftruncate(wfd, body_len);
+			       if (body_len)
+				       sys_ftruncate(wfd, body_len);
				vcollected = kstrdup(collected, GFP_KERNEL);
				state = CopyFile;
			}