From 8d3ae59dee2930d640add3bba983006e1f5dd1b6 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 14:34:58 +1100
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Subject: [PATCH] fs/sfs: Fix over-read of root object name
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There's a read of the name of the root object that assumes that the name
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is nul-terminated within the root block. This isn't guaranteed - it seems
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SFS would require you to read multiple blocks to get a full name in general,
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but maybe that doesn't apply to the root object.
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Either way, figure out how much space is left in the root block and don't
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over-read it. This fixes some OOB reads.
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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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Signed-off-by: Stefan Sørensen <stefan.sorensen@spectralink.com>
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---
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grub-core/fs/sfs.c | 9 ++++++++-
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1 file changed, 8 insertions(+), 1 deletion(-)
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diff --git a/grub-core/fs/sfs.c b/grub-core/fs/sfs.c
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index de2b107..983e880 100644
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--- a/grub-core/fs/sfs.c
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+++ b/grub-core/fs/sfs.c
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@@ -373,6 +373,7 @@ grub_sfs_mount (grub_disk_t disk)
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struct grub_sfs_objc *rootobjc;
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char *rootobjc_data = 0;
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grub_uint32_t blk;
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+ unsigned int max_len;
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data = grub_malloc (sizeof (*data));
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if (!data)
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@@ -421,7 +422,13 @@ grub_sfs_mount (grub_disk_t disk)
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data->diropen.data = data;
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data->diropen.cache = 0;
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data->disk = disk;
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- data->label = grub_strdup ((char *) (rootobjc->objects[0].filename));
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+
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+ /* We only read 1 block of data, so truncate the name if needed. */
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+ max_len = ((GRUB_DISK_SECTOR_SIZE << data->log_blocksize)
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+ - 24 /* offsetof (struct grub_sfs_objc, objects) */
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+ - 25); /* offsetof (struct grub_sfs_obj, filename) */
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+ data->label = grub_zalloc (max_len + 1);
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+ grub_strncpy (data->label, (char *) rootobjc->objects[0].filename, max_len);
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grub_free (rootobjc_data);
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return data;
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--
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2.14.2
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