86 lines
2.8 KiB
Diff
86 lines
2.8 KiB
Diff
From 6d056d620ff6a61c84269f0cf71003829ffecd6a Mon Sep 17 00:00:00 2001
|
|
From: Dimitri John Ledkov <xnox@ubuntu.com>
|
|
Date: Thu, 14 Jan 2021 20:02:56 +0000
|
|
Subject: [PATCH] lib/decompress_unlz4.c: correctly handle zero-padding around
|
|
initrds.
|
|
|
|
lz4 compatible decompressor is simple. The format is underspecified and
|
|
relies on EOF notification to determine when to stop. Initramfs buffer
|
|
format[1] explicitly states that it can have arbitrary number of zero
|
|
padding. Thus when operating without a fill function, be extra careful to
|
|
ensure that sizes less than 4, or apperantly empty chunksizes are treated
|
|
as EOF.
|
|
|
|
To test this I have created two cpio initrds, first a normal one,
|
|
main.cpio. And second one with just a single /test-file with content
|
|
"second" second.cpio. Then i compressed both of them with gzip, and with
|
|
lz4 -l. Then I created a padding of 4 bytes (dd if=/dev/zero of=pad4 bs=1
|
|
count=4). To create four testcase initrds:
|
|
|
|
1) main.cpio.gzip + extra.cpio.gzip = pad0.gzip
|
|
2) main.cpio.lz4 + extra.cpio.lz4 = pad0.lz4
|
|
3) main.cpio.gzip + pad4 + extra.cpio.gzip = pad4.gzip
|
|
4) main.cpio.lz4 + pad4 + extra.cpio.lz4 = pad4.lz4
|
|
|
|
The pad4 test-cases replicate the initrd load by grub, as it pads and
|
|
aligns every initrd it loads.
|
|
|
|
All of the above boot, however /test-file was not accessible in the initrd
|
|
for the testcase #4, as decoding in lz4 decompressor failed. Also an error
|
|
message printed which usually is harmless.
|
|
|
|
Whith a patched kernel, all of the above testcases now pass, and /test-file
|
|
is accessible.
|
|
|
|
This fixes lz4 initrd decompress warning on every boot with grub. And more
|
|
importantly this fixes inability to load multiple lz4 compressed initrds
|
|
with grub.
|
|
|
|
I guess I should convert above decompressor streams with/without padding
|
|
into kunit tests, across all decompressor algorithms.
|
|
|
|
[1] ./Documentation/driver-api/early-userspace/buffer-format.rst
|
|
|
|
BugLink: https://bugs.launchpad.net/bugs/1835660
|
|
Signed-off-by: Dimitri John Ledkov <xnox@ubuntu.com>
|
|
---
|
|
lib/decompress_unlz4.c | 8 ++++++++
|
|
1 file changed, 8 insertions(+)
|
|
|
|
diff --git a/lib/decompress_unlz4.c b/lib/decompress_unlz4.c
|
|
index c0cfcfd486be..e6327391b6b6 100644
|
|
--- a/lib/decompress_unlz4.c
|
|
+++ b/lib/decompress_unlz4.c
|
|
@@ -112,6 +112,9 @@ STATIC inline int INIT unlz4(u8 *input, long in_len,
|
|
error("data corrupted");
|
|
goto exit_2;
|
|
}
|
|
+ } else if (size < 4) {
|
|
+ /* empty or end-of-file */
|
|
+ goto exit_3;
|
|
}
|
|
|
|
chunksize = get_unaligned_le32(inp);
|
|
@@ -125,6 +128,10 @@ STATIC inline int INIT unlz4(u8 *input, long in_len,
|
|
continue;
|
|
}
|
|
|
|
+ if (!fill && chunksize == 0) {
|
|
+ /* empty or end-of-file */
|
|
+ goto exit_3;
|
|
+ }
|
|
|
|
if (posp)
|
|
*posp += 4;
|
|
@@ -184,6 +191,7 @@ STATIC inline int INIT unlz4(u8 *input, long in_len,
|
|
}
|
|
}
|
|
|
|
+exit_3:
|
|
ret = 0;
|
|
exit_2:
|
|
if (!input)
|
|
--
|
|
2.31.1
|
|
|