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grub2/SOURCES/0442-fs-sfs-Fix-over-read-o...

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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Daniel Axtens <dja@axtens.net>
Date: Mon, 18 Jan 2021 14:34:58 +1100
Subject: [PATCH] fs/sfs: Fix over-read of root object name
There's a read of the name of the root object that assumes that the name
is nul-terminated within the root block. This isn't guaranteed - it seems
SFS would require you to read multiple blocks to get a full name in general,
but maybe that doesn't apply to the root object.
Either way, figure out how much space is left in the root block and don't
over-read it. This fixes some OOB reads.
Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
grub-core/fs/sfs.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/grub-core/fs/sfs.c b/grub-core/fs/sfs.c
index 3ddc6b5e2..61d6c303c 100644
--- a/grub-core/fs/sfs.c
+++ b/grub-core/fs/sfs.c
@@ -373,6 +373,7 @@ grub_sfs_mount (grub_disk_t disk)
struct grub_sfs_objc *rootobjc;
char *rootobjc_data = 0;
grub_uint32_t blk;
+ unsigned int max_len;
data = grub_malloc (sizeof (*data));
if (!data)
@@ -421,7 +422,13 @@ grub_sfs_mount (grub_disk_t disk)
data->diropen.data = data;
data->diropen.cache = 0;
data->disk = disk;
- data->label = grub_strdup ((char *) (rootobjc->objects[0].filename));
+
+ /* We only read 1 block of data, so truncate the name if needed. */
+ max_len = ((GRUB_DISK_SECTOR_SIZE << data->log_blocksize)
+ - 24 /* offsetof (struct grub_sfs_objc, objects) */
+ - 25); /* offsetof (struct grub_sfs_obj, filename) */
+ data->label = grub_zalloc (max_len + 1);
+ grub_strncpy (data->label, (char *) rootobjc->objects[0].filename, max_len);
grub_free (rootobjc_data);
return data;