fs/xfs: Re-apply the XFS directory extent parsing patch

Resolves: #2259266
Signed-off-by: Nicolas Frayer <nfrayer@redhat.com>

0352-fs-xfs-Fix-XFS-directory-extent-parsing.patch

@@ -0,0 +1,168 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Jon DeVree <nuxi@vault24.org>
+Date: Tue, 17 Oct 2023 23:03:47 -0400
+Subject: [PATCH] fs/xfs: Fix XFS directory extent parsing
+
+The XFS directory entry parsing code has never been completely correct
+for extent based directories. The parser correctly handles the case
+where the directory is contained in a single extent, but then mistakenly
+assumes the data blocks for the multiple extent case are each identical
+to the single extent case. The difference in the format of the data
+blocks between the two cases is tiny enough that its gone unnoticed for
+a very long time.
+
+A recent change introduced some additional bounds checking into the XFS
+parser. Like GRUB's existing parser, it is correct for the single extent
+case but incorrect for the multiple extent case. When parsing a directory
+with multiple extents, this new bounds checking is sometimes (but not
+always) tripped and triggers an "invalid XFS directory entry" error. This
+probably would have continued to go unnoticed but the /boot/grub/<arch>
+directory is large enough that it often has multiple extents.
+
+The difference between the two cases is that when there are multiple
+extents, the data blocks do not contain a trailer nor do they contain
+any leaf information. That information is stored in a separate set of
+extents dedicated to just the leaf information. These extents come after
+the directory entry extents and are not included in the inode size. So
+the existing parser already ignores the leaf extents.
+
+The only reason to read the trailer/leaf information at all is so that
+the parser can avoid misinterpreting that data as directory entries. So
+this updates the parser as follows:
+
+For the single extent case the parser doesn't change much:
+1. Read the size of the leaf information from the trailer
+2. Set the end pointer for the parser to the start of the leaf
+   information. (The previous bounds checking set the end pointer to the
+   start of the trailer, so this is actually a small improvement.)
+3. Set the entries variable to the expected number of directory entries.
+
+For the multiple extent case:
+1. Set the end pointer to the end of the block.
+2. Do not set up the entries variable. Figuring out how many entries are
+   in each individual block is complex and does not seem worth it when
+   it appears to be safe to just iterate over the entire block.
+
+The bounds check itself was also dependent upon the faulty XFS parser
+because it accidentally used "filename + length - 1". Presumably this
+was able to pass the fuzzer because in the old parser there was always
+8 bytes of slack space between the tail pointer and the actual end of
+the block. Since this is no longer the case the bounds check needs to be
+updated to "filename + length + 1" in order to prevent a regression in
+the handling of corrupt fliesystems.
+
+Notes:
+* When there is only one extent there will only ever be one block. If
+  more than one block is required then XFS will always switch to holding
+  leaf information in a separate extent.
+* B-tree based directories seems to be parsed properly by the same code
+  that handles multiple extents. This is unlikely to ever occur within
+  /boot though because its only used when there are an extremely large
+  number of directory entries.
+
+Fixes: ef7850c75 (fs/xfs: Fix issues found while fuzzing the XFS filesystem)
+Fixes: b2499b29c (Adds support for the XFS filesystem.)
+Fixes: https://savannah.gnu.org/bugs/?64376
+
+Signed-off-by: Jon DeVree <nuxi@vault24.org>
+Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
+Tested-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
+Tested-by: Marta Lewandowska <mlewando@redhat.com>
+---
+ grub-core/fs/xfs.c | 52 ++++++++++++++++++++++++++++++++++++++--------------
+ 1 file changed, 38 insertions(+), 14 deletions(-)
+
+diff --git a/grub-core/fs/xfs.c b/grub-core/fs/xfs.c
+index ebf962793fa7..18edfcff486c 100644
+--- a/grub-core/fs/xfs.c
++++ b/grub-core/fs/xfs.c
+@@ -223,6 +223,12 @@ struct grub_xfs_inode
+ /* Size of struct grub_xfs_inode v2, up to unused4 member included. */
+ #define XFS_V2_INODE_SIZE	(XFS_V3_INODE_SIZE - 76)
+ 
++struct grub_xfs_dir_leaf_entry
++{
++  grub_uint32_t hashval;
++  grub_uint32_t address;
++} GRUB_PACKED;
++
+ struct grub_xfs_dirblock_tail
+ {
+   grub_uint32_t leaf_count;
+@@ -874,9 +880,8 @@ grub_xfs_iterate_dir (grub_fshelp_node_t dir,
+ 	  {
+ 	    struct grub_xfs_dir2_entry *direntry =
+ 					grub_xfs_first_de(dir->data, dirblock);
+-	    int entries;
+-	    struct grub_xfs_dirblock_tail *tail =
+-					grub_xfs_dir_tail(dir->data, dirblock);
++	    int entries = -1;
++	    char *end = dirblock + dirblk_size;
+ 
+ 	    numread = grub_xfs_read_file (dir, 0, 0,
+ 					  blk << dirblk_log2,
+@@ -887,14 +892,27 @@ grub_xfs_iterate_dir (grub_fshelp_node_t dir,
+ 	        return 0;
+ 	      }
+ 
+-	    entries = (grub_be_to_cpu32 (tail->leaf_count)
+-		       - grub_be_to_cpu32 (tail->leaf_stale));
++	    /*
++	     * Leaf and tail information are only in the data block if the number
++	     * of extents is 1.
++	     */
++	    if (dir->inode.nextents == grub_cpu_to_be32_compile_time (1))
++	      {
++		struct grub_xfs_dirblock_tail *tail = grub_xfs_dir_tail (dir->data, dirblock);
+ 
+-	    if (!entries)
+-	      continue;
++		end = (char *) tail;
++
++		/* Subtract the space used by leaf nodes. */
++		end -= grub_be_to_cpu32 (tail->leaf_count) * sizeof (struct grub_xfs_dir_leaf_entry);
++
++		entries = grub_be_to_cpu32 (tail->leaf_count) - grub_be_to_cpu32 (tail->leaf_stale);
++
++		if (!entries)
++		  continue;
++	      }
+ 
+ 	    /* Iterate over all entries within this block.  */
+-	    while ((char *)direntry < (char *)tail)
++	    while ((char *) direntry < (char *) end)
+ 	      {
+ 		grub_uint8_t *freetag;
+ 		char *filename;
+@@ -914,7 +932,7 @@ grub_xfs_iterate_dir (grub_fshelp_node_t dir,
+ 		  }
+ 
+ 		filename = (char *)(direntry + 1);
+-		if (filename + direntry->len - 1 > (char *) tail)
++		if (filename + direntry->len + 1 > (char *) end)
+ 		  return grub_error (GRUB_ERR_BAD_FS, "invalid XFS directory entry");
+ 
+ 		/* The byte after the filename is for the filetype, padding, or
+@@ -928,11 +946,17 @@ grub_xfs_iterate_dir (grub_fshelp_node_t dir,
+ 		    return 1;
+ 		  }
+ 
+-		/* Check if last direntry in this block is
+-		   reached.  */
+-		entries--;
+-		if (!entries)
+-		  break;
++		/*
++		 * The expected number of directory entries is only tracked for the
++		 * single extent case.
++		 */
++		if (dir->inode.nextents == grub_cpu_to_be32_compile_time (1))
++		  {
++		    /* Check if last direntry in this block is reached. */
++		    entries--;
++		    if (!entries)
++		      break;
++		  }
+ 
+ 		/* Select the next directory entry.  */
+ 		direntry = grub_xfs_next_de(dir->data, direntry);

grub.patches

@@ -349,3 +349,4 @@ Patch0348: 0348-add-flag-to-only-search-root-dev.patch
 Patch0349: 0349-grub-set-bootflag-Conservative-partial-fix-for-CVE-2.patch
 Patch0350: 0350-grub-set-bootflag-More-complete-fix-for-CVE-2024-104.patch
 Patch0351: 0351-grub-set-bootflag-Exit-calmly-when-not-running-as-ro.patch
+Patch0352: 0352-fs-xfs-Fix-XFS-directory-extent-parsing.patch

grub2.spec

@@ -17,7 +17,7 @@
 Name:		grub2
 Epoch:		1
 Version:	2.06
-Release:	117%{?dist}
+Release:	118%{?dist}
 Summary:	Bootloader with support for Linux, Multiboot and more
 License:	GPLv3+
 URL:		http://www.gnu.org/software/grub/
@@ -554,6 +554,10 @@ mv ${EFI_HOME}/grub.cfg.stb ${EFI_HOME}/grub.cfg
 %endif
 
 %changelog
+* Wed Feb 7 2024 Nicolas Frayer <nfrayer@redhat.com> - 2.06-118
+- fs/xfs: Re-applied the XFS directory extent parsing patch
+- Resolves: #2259266
+
 * Wed Feb 7 2024 Nicolas Frayer <nfrayer@redhat.com> - 2.06-117
 - grub-set-bootflag: Fix for CVE-2024-1048
 - (CVE-2024-1048)