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erofs: avoid using multiple devices with different type

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For multiple devices, both primary and extra devices should be the
same type. `erofs_init_device` has already guaranteed that if the
primary is a file-backed device, extra devices should also be
regular files.

However, if the primary is a block device while the extra device
is a file-backed device, `erofs_init_device` will get an ENOTBLK,
which is not treated as an error in `erofs_fc_get_tree`, and that
leads to an UAF:

  erofs_fc_get_tree
    get_tree_bdev_flags(erofs_fc_fill_super)
      erofs_read_superblock
        erofs_init_device  // sbi->dif0 is not inited yet,
                           // return -ENOTBLK
      deactivate_locked_super
        free(sbi)
    if (err is -ENOTBLK)
      sbi->dif0.file = filp_open()  // sbi UAF

So if -ENOTBLK is hitted in `erofs_init_device`, it means the
primary device must be a block device, and the extra device
is not a block device. The error can be converted to -EINVAL.

Fixes: fb17675026 ("erofs: add file-backed mount support")
Signed-off-by: Sheng Yong <shengyong1@xiaomi.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Hongbo Li <lihongbo22@huawei.com>
Link: https://lore.kernel.org/r/20250515014837.3315886-1-shengyong1@xiaomi.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
This commit is contained in:
Sheng Yong 2025-05-15 09:48:37 +08:00 • committed by Gao Xiang
parent 510de8363f
commit 9748f2f54f
1 changed files with 4 additions and 1 deletions
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5
fs/erofs/super.c
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@ -165,8 +165,11 @@ static int erofs_init_device(struct erofs_buf *buf, struct super_block *sb,
filp_open(dif->path, O_RDONLY | O_LARGEFILE, 0) :
bdev_file_open_by_path(dif->path,
BLK_OPEN_READ, sb->s_type, NULL);
if (IS_ERR(file))
if (IS_ERR(file)) {
if (file == ERR_PTR(-ENOTBLK))
return -EINVAL;
return PTR_ERR(file);
}
if (!erofs_is_fileio_mode(sbi)) {
dif->dax_dev = fs_dax_get_by_bdev(file_bdev(file),