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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Daniel Axtens <dja@axtens.net>
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Date: Mon, 18 Jan 2021 15:47:24 +1100
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Subject: [PATCH] fs/jfs: Catch infinite recursion
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It's possible with a fuzzed filesystem for JFS to keep getblk()-ing
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the same data over and over again, leading to stack exhaustion.
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Check if we'd be calling the function with exactly the same data as
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was passed in, and if so abort.
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I'm not sure what the performance impact of this is and am open to
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better ideas.
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Signed-off-by: Daniel Axtens <dja@axtens.net>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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---
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grub-core/fs/jfs.c | 11 ++++++++++-
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1 file changed, 10 insertions(+), 1 deletion(-)
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diff --git a/grub-core/fs/jfs.c b/grub-core/fs/jfs.c
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index 6e81f37da..20d966abf 100644
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--- a/grub-core/fs/jfs.c
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+++ b/grub-core/fs/jfs.c
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@@ -304,7 +304,16 @@ getblk (struct grub_jfs_treehead *treehead,
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<< (grub_le_to_cpu16 (data->sblock.log2_blksz)
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- GRUB_DISK_SECTOR_BITS), 0,
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sizeof (*tree), (char *) tree))
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- ret = getblk (&tree->treehead, &tree->extents[0], 254, data, blk);
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+ {
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+ if (grub_memcmp (&tree->treehead, treehead, sizeof (struct grub_jfs_treehead)) ||
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+ grub_memcmp (&tree->extents, extents, 254 * sizeof (struct grub_jfs_tree_extent)))
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+ ret = getblk (&tree->treehead, &tree->extents[0], 254, data, blk);
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+ else
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+ {
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+ grub_error (GRUB_ERR_BAD_FS, "jfs: infinite recursion detected");
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+ ret = -1;
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+ }
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+ }
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grub_free (tree);
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return ret;
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}
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