From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jon DeVree <nuxi@vault24.org>
Date: Sun, 11 Feb 2024 10:34:58 -0500
Subject: [PATCH] fs/xfs: Handle non-continuous data blocks in directory
extents
The directory extent list does not have to be a continuous list of data
blocks. When GRUB tries to read a non-existant member of the list,
grub_xfs_read_file() will return a block of zero'ed memory. Checking for
a zero'ed magic number is sufficient to skip this non-existant data block.
Prior to commit 07318ee7e (fs/xfs: Fix XFS directory extent parsing)
this was handled as a subtle side effect of reading the (non-existant)
tail data structure. Since the block was zero'ed the computation of the
number of directory entries in the block would return 0 as well.
Fixes: 07318ee7e (fs/xfs: Fix XFS directory extent parsing)
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2254370
Signed-off-by: Jon DeVree <nuxi@vault24.org>
Reviewed-By: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
grub-core/fs/xfs.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/grub-core/fs/xfs.c b/grub-core/fs/xfs.c
index bc2224dbb463..8e02ab4a3014 100644
--- a/grub-core/fs/xfs.c
+++ b/grub-core/fs/xfs.c
@@ -902,6 +902,7 @@ grub_xfs_iterate_dir (grub_fshelp_node_t dir,
grub_xfs_first_de(dir->data, dirblock);
int entries = -1;
char *end = dirblock + dirblk_size;
+ grub_uint32_t magic;
numread = grub_xfs_read_file (dir, 0, 0,
blk << dirblk_log2,
@@ -912,6 +913,15 @@ grub_xfs_iterate_dir (grub_fshelp_node_t dir,
return 0;
}
+ /*
+ * If this data block isn't actually part of the extent list then
+ * grub_xfs_read_file() returns a block of zeros. So, if the magic
+ * number field is all zeros then this block should be skipped.
+ */
+ magic = *(grub_uint32_t *)(void *) dirblock;
+ if (!magic)
+ continue;
+
/*
* Leaf and tail information are only in the data block if the number
* of extents is 1.