From 8d3ae59dee2930d640add3bba983006e1f5dd1b6 Mon Sep 17 00:00:00 2001 From: Daniel Axtens 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 Reviewed-by: Daniel Kiper Signed-off-by: Stefan Sørensen --- 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 de2b107..983e880 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; -- 2.14.2