linux-kernel - [PATCH] init: open output files from cpio unpacking with O

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Message-ID: <20240323152934.3307391-1-jsperbeck@google.com>
Date: Sat, 23 Mar 2024 08:29:34 -0700
From: John Sperbeck <jsperbeck@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>, Jens Axboe <axboe@...nel.dk>, 
	"Peter Zijlstra (Intel)" <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>, 
	"ndesaulniers@...gle.com" <ndesaulniers@...gle.com>
Cc: Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org, 
	John Sperbeck <jsperbeck@...gle.com>
Subject: [PATCH] init: open output files from cpio unpacking with O_LARGEFILE

If a member of a cpio archive for an initrd or initrams is larger
than 2Gb, we'll eventually fail to write to that file when we
get to that limit, unless O_LARGEFILE is set.

The problem can be seen with this recipe, assuming that BLK_DEV_RAM
is not configured:

cd /tmp
dd if=/dev/zero of=BIGFILE bs=1048576 count=2200
echo BIGFILE | cpio -o -H newc -R root:root > initrd.img
kexec -l /boot/vmlinuz-$(uname -r) --initrd=initrd.img --reuse-cmdline
kexec -e

The console will show 'Initramfs unpacking failed: write error'.  With
the patch, the error is gone.

Signed-off-by: John Sperbeck <jsperbeck@...gle.com>
---
 init/initramfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/init/initramfs.c b/init/initramfs.c
index 76deb48c38cb..b5ede45d2f7e 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -366,7 +366,7 @@ static int __init do_name(void)
 	if (S_ISREG(mode)) {
 		int ml = maybe_link();
 		if (ml >= 0) {
-			int openflags = O_WRONLY|O_CREAT;
+			int openflags = O_WRONLY|O_CREAT|O_LARGEFILE;
 			if (ml != 1)
 				openflags |= O_TRUNC;
 			wfile = filp_open(collected, openflags, mode);
-- 
2.44.0.396.g6e790dbe36-goog