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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Darren Kenny <darren.kenny@oracle.com>
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Date: Thu, 7 Apr 2022 15:18:12 +0000
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Subject: [PATCH] fs/btrfs: Fix more fuzz issues related to chunks
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The corpus we generating issues in grub_btrfs_read_logical() when
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attempting to iterate over nstripes entries in the boot mapping.
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In most cases the reason for the failure was that the number of strips
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exceeded the possible space statically allocated in superblock bootmapping
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space. Each stripe entry in the bootmapping block consists of
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a grub_btrfs_key followed by a grub_btrfs_chunk_stripe.
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Another issue that came up was that while calculating the chunk size,
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in an earlier piece of code in that function, depending on the data
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provided in the btrfs file system, it would end up calculating a size
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that was too small to contain even 1 grub_btrfs_chunk_item, which is
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obviously invalid too.
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Signed-off-by: Darren Kenny <darren.kenny@oracle.com>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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(cherry picked from commit e00cd76cbadcc897a9cc4087cb2fcb5dbe15e596)
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---
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grub-core/fs/btrfs.c | 24 ++++++++++++++++++++++++
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1 file changed, 24 insertions(+)
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diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
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index 0e9b450413..47325f6ad7 100644
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--- a/grub-core/fs/btrfs.c
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+++ b/grub-core/fs/btrfs.c
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@@ -947,6 +947,17 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
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return grub_error (GRUB_ERR_BAD_FS,
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"got an invalid zero-size chunk");
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}
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+
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+ /*
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+ * The space being allocated for a chunk should at least be able to
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+ * contain one chunk item.
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+ */
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+ if (chsize < sizeof (struct grub_btrfs_chunk_item))
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+ {
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+ grub_dprintf ("btrfs", "chunk-size too small\n");
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+ return grub_error (GRUB_ERR_BAD_FS,
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+ "got an invalid chunk size");
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+ }
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chunk = grub_malloc (chsize);
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if (!chunk)
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return grub_errno;
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@@ -1194,6 +1205,13 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
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if (csize > (grub_uint64_t) size)
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csize = size;
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+ /*
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+ * The space for a chunk stripe is limited to the space provide in the super-block's
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+ * bootstrap mapping with an initial btrfs key at the start of each chunk.
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+ */
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+ grub_size_t avail_stripes = sizeof (data->sblock.bootstrap_mapping) /
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+ (sizeof (struct grub_btrfs_key) + sizeof (struct grub_btrfs_chunk_stripe));
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+
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for (j = 0; j < 2; j++)
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{
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grub_size_t est_chunk_alloc = 0;
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@@ -1220,6 +1238,12 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
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break;
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}
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+ if (grub_le_to_cpu16 (chunk->nstripes) > avail_stripes)
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+ {
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+ err = GRUB_ERR_BAD_FS;
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+ break;
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+ }
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+
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if (is_raid56)
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{
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err = btrfs_read_from_chunk (data, chunk, stripen,
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