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@@ -1,168 +0,0 @@
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- From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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- From: Jon DeVree <nuxi@vault24.org>
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- Date: Tue, 17 Oct 2023 23:03:47 -0400
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- Subject: [PATCH] fs/xfs: Fix XFS directory extent parsing
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-
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- The XFS directory entry parsing code has never been completely correct
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- for extent based directories. The parser correctly handles the case
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- where the directory is contained in a single extent, but then mistakenly
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- assumes the data blocks for the multiple extent case are each identical
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- to the single extent case. The difference in the format of the data
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- blocks between the two cases is tiny enough that its gone unnoticed for
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- a very long time.
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-
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- A recent change introduced some additional bounds checking into the XFS
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- parser. Like GRUB's existing parser, it is correct for the single extent
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- case but incorrect for the multiple extent case. When parsing a directory
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- with multiple extents, this new bounds checking is sometimes (but not
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- always) tripped and triggers an "invalid XFS directory entry" error. This
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- probably would have continued to go unnoticed but the /boot/grub/<arch>
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- directory is large enough that it often has multiple extents.
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-
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- The difference between the two cases is that when there are multiple
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- extents, the data blocks do not contain a trailer nor do they contain
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- any leaf information. That information is stored in a separate set of
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- extents dedicated to just the leaf information. These extents come after
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- the directory entry extents and are not included in the inode size. So
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- the existing parser already ignores the leaf extents.
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-
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- The only reason to read the trailer/leaf information at all is so that
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- the parser can avoid misinterpreting that data as directory entries. So
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- this updates the parser as follows:
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-
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- For the single extent case the parser doesn't change much:
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- 1. Read the size of the leaf information from the trailer
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- 2. Set the end pointer for the parser to the start of the leaf
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- information. (The previous bounds checking set the end pointer to the
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- start of the trailer, so this is actually a small improvement.)
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- 3. Set the entries variable to the expected number of directory entries.
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-
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- For the multiple extent case:
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- 1. Set the end pointer to the end of the block.
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- 2. Do not set up the entries variable. Figuring out how many entries are
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- in each individual block is complex and does not seem worth it when
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- it appears to be safe to just iterate over the entire block.
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-
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- The bounds check itself was also dependent upon the faulty XFS parser
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- because it accidentally used "filename + length - 1". Presumably this
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- was able to pass the fuzzer because in the old parser there was always
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- 8 bytes of slack space between the tail pointer and the actual end of
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- the block. Since this is no longer the case the bounds check needs to be
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- updated to "filename + length + 1" in order to prevent a regression in
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- the handling of corrupt fliesystems.
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-
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- Notes:
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- * When there is only one extent there will only ever be one block. If
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- more than one block is required then XFS will always switch to holding
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- leaf information in a separate extent.
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- * B-tree based directories seems to be parsed properly by the same code
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- that handles multiple extents. This is unlikely to ever occur within
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- /boot though because its only used when there are an extremely large
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- number of directory entries.
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-
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- Fixes: ef7850c75 (fs/xfs: Fix issues found while fuzzing the XFS filesystem)
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- Fixes: b2499b29c (Adds support for the XFS filesystem.)
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- Fixes: https://savannah.gnu.org/bugs/?64376
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-
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- Signed-off-by: Jon DeVree <nuxi@vault24.org>
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- Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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- Tested-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
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- Tested-by: Marta Lewandowska <mlewando@redhat.com>
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- ---
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- grub-core/fs/xfs.c | 52 ++++++++++++++++++++++++++++++++++++++--------------
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- 1 file changed, 38 insertions(+), 14 deletions(-)
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-
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- diff --git a/grub-core/fs/xfs.c b/grub-core/fs/xfs.c
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- index ebf962793fa7..18edfcff486c 100644
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- --- a/grub-core/fs/xfs.c
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- +++ b/grub-core/fs/xfs.c
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- @@ -223,6 +223,12 @@ struct grub_xfs_inode
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- /* Size of struct grub_xfs_inode v2, up to unused4 member included. */
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- #define XFS_V2_INODE_SIZE (XFS_V3_INODE_SIZE - 76)
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-
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- +struct grub_xfs_dir_leaf_entry
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- +{
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- + grub_uint32_t hashval;
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- + grub_uint32_t address;
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- +} GRUB_PACKED;
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- +
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- struct grub_xfs_dirblock_tail
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- {
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- grub_uint32_t leaf_count;
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- @@ -874,9 +880,8 @@ grub_xfs_iterate_dir (grub_fshelp_node_t dir,
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- {
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- struct grub_xfs_dir2_entry *direntry =
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- grub_xfs_first_de(dir->data, dirblock);
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- - int entries;
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- - struct grub_xfs_dirblock_tail *tail =
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- - grub_xfs_dir_tail(dir->data, dirblock);
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- + int entries = -1;
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- + char *end = dirblock + dirblk_size;
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-
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- numread = grub_xfs_read_file (dir, 0, 0,
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- blk << dirblk_log2,
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- @@ -887,14 +892,27 @@ grub_xfs_iterate_dir (grub_fshelp_node_t dir,
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- return 0;
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- }
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-
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- - entries = (grub_be_to_cpu32 (tail->leaf_count)
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- - - grub_be_to_cpu32 (tail->leaf_stale));
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- + /*
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- + * Leaf and tail information are only in the data block if the number
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- + * of extents is 1.
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- + */
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- + if (dir->inode.nextents == grub_cpu_to_be32_compile_time (1))
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- + {
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- + struct grub_xfs_dirblock_tail *tail = grub_xfs_dir_tail (dir->data, dirblock);
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-
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- - if (!entries)
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- - continue;
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- + end = (char *) tail;
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- +
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- + /* Subtract the space used by leaf nodes. */
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- + end -= grub_be_to_cpu32 (tail->leaf_count) * sizeof (struct grub_xfs_dir_leaf_entry);
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- +
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- + entries = grub_be_to_cpu32 (tail->leaf_count) - grub_be_to_cpu32 (tail->leaf_stale);
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- +
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- + if (!entries)
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- + continue;
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- + }
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-
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- /* Iterate over all entries within this block. */
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- - while ((char *)direntry < (char *)tail)
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- + while ((char *) direntry < (char *) end)
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- {
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- grub_uint8_t *freetag;
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- char *filename;
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- @@ -914,7 +932,7 @@ grub_xfs_iterate_dir (grub_fshelp_node_t dir,
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- }
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-
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- filename = (char *)(direntry + 1);
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- - if (filename + direntry->len - 1 > (char *) tail)
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- + if (filename + direntry->len + 1 > (char *) end)
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- return grub_error (GRUB_ERR_BAD_FS, "invalid XFS directory entry");
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-
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- /* The byte after the filename is for the filetype, padding, or
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- @@ -928,11 +946,17 @@ grub_xfs_iterate_dir (grub_fshelp_node_t dir,
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- return 1;
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- }
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-
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- - /* Check if last direntry in this block is
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- - reached. */
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- - entries--;
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- - if (!entries)
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- - break;
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- + /*
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- + * The expected number of directory entries is only tracked for the
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- + * single extent case.
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- + */
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- + if (dir->inode.nextents == grub_cpu_to_be32_compile_time (1))
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- + {
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- + /* Check if last direntry in this block is reached. */
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- + entries--;
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- + if (!entries)
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- + break;
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- + }
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-
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- /* Select the next directory entry. */
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- direntry = grub_xfs_next_de(dir->data, direntry);
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Some bios systems with /boot partition created with
xfsprog < 6.5.0 can't boot with one of the xfs upstream patches
Resolves: #2254370
Signed-off-by: Nicolas Frayer nfrayer@redhat.com