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authorLoic Poulain <loic.poulain@linaro.org>2023-05-10 09:42:23 +0200
committerJens Axboe <axboe@kernel.dk>2023-05-19 20:17:10 -0600
commit69baa3a623fd2e58624f24f2f23d46f87b817c93 (patch)
treec12d32ab13e9a1283dcb8701fd3f2065b06255e4
parentc99bff34290f1b994073557b754aff86e4c7b22e (diff)
block: Deny writable memory mapping if block is read-only
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 a32e236eb93e ("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>
-rw-r--r--block/fops.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/block/fops.c b/block/fops.c
index d2e6be4e3d1c..58d0aebc7313 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -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