Kernel/linux
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2024-12-29 09:13:38 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

block: Deny writable memory mapping if block is read-only

Browse Source 
User should not be able to write block device if it is read-only at
block level (e.g force_ro attribute). This is ensured in the regular
fops write operation (blkdev_write_iter) but not when writing via
user mapping (mmap), allowing user to actually write a read-only
block device via a PROT_WRITE mapping.

Example: This can lead to integrity issue of eMMC boot partition
(e.g mmcblk0boot0) which is read-only by default.

To fix this issue, simply deny shared writable mapping if the block
is readonly.

Note: Block remains writable if switch to read-only is performed
after the initial mapping, but this is expected behavior according
to commit a32e236eb9 ("Partially revert "block: fail op_is_write()
requests to read-only partitions"")'.

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230510074223.991297-1-loic.poulain@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Loic Poulain 2023-05-10 09:42:23 +02:00 committed by Jens Axboe
parent c99bff3429
commit 69baa3a623
1 changed files with 11 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
block/fops.c
View File

@ -678,6 +678,16 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
return error;
}
static int blkdev_mmap(struct file *file, struct vm_area_struct *vma)
{
struct inode *bd_inode = bdev_file_inode(file);
if (bdev_read_only(I_BDEV(bd_inode)))
return generic_file_readonly_mmap(file, vma);
return generic_file_mmap(file, vma);
}
const struct file_operations def_blk_fops = {
.open = blkdev_open,
.release = blkdev_close,
@ -685,7 +695,7 @@ const struct file_operations def_blk_fops = {
.read_iter = blkdev_read_iter,
.write_iter = blkdev_write_iter,
.iopoll = iocb_bio_iopoll,
.mmap = generic_file_mmap,
.mmap = blkdev_mmap,
.fsync = blkdev_fsync,
.unlocked_ioctl = blkdev_ioctl,
#ifdef CONFIG_COMPAT