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block: Ensure probing reads are block size aligned

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This is necessary for O_DIRECT based use of raw block devices which may
require access at a larger block size than that of a sector (512 bytes.)

Fixes: #5722

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>
This commit is contained in:
Rob Bradford
2023-09-03 12:00:30 +01:00
committed by Bo Chen
parent 9ca2c336f2
commit 01097aa130
2 changed files with 45 additions and 39 deletions
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53
block/src/vhd.rs
View File

@@ -2,9 +2,10 @@
//
// SPDX-License-Identifier: Apache-2.0
use crate::{read_aligned_block_size, DiskTopology};
use std::convert::TryInto;
use std::fs::File;
use std::io::{Read, Seek, SeekFrom};
use std::io::{Seek, SeekFrom};
#[derive(Clone, Copy)]
pub struct VhdFooter {
@@ -27,37 +28,33 @@ pub struct VhdFooter {
impl VhdFooter {
pub fn new(file: &mut File) -> std::io::Result<VhdFooter> {
// We must create a buffer aligned on 512 bytes with a size being a
// multiple of 512 bytes as the file might be opened with O_DIRECT flag.
#[repr(align(512))]
struct Sector {
data: [u8; 512],
}
let mut s = Sector { data: [0; 512] };
let blocksize = DiskTopology::probe(file)?.logical_block_size as usize;
// Place the cursor 512 bytes before the end of the file, as this is
// where the footer starts.
file.seek(SeekFrom::End(-512))?;
// Place the cursor in the last block of the file
file.seek(SeekFrom::End(0 - (blocksize as i64)))?;
// Read in the last block
let data = read_aligned_block_size(file)?;
// Fill in the VhdFooter structure
file.read_exact(&mut s.data)?;
// We only care about the last sector
let offset = blocksize - 512;
let sector = &data[offset..];
Ok(VhdFooter {
cookie: u64::from_be_bytes(s.data[0..8].try_into().unwrap()),
features: u32::from_be_bytes(s.data[8..12].try_into().unwrap()),
file_format_version: u32::from_be_bytes(s.data[12..16].try_into().unwrap()),
data_offset: u64::from_be_bytes(s.data[16..24].try_into().unwrap()),
time_stamp: u32::from_be_bytes(s.data[24..28].try_into().unwrap()),
creator_application: u32::from_be_bytes(s.data[28..32].try_into().unwrap()),
creator_version: u32::from_be_bytes(s.data[32..36].try_into().unwrap()),
creator_host_os: u32::from_be_bytes(s.data[36..40].try_into().unwrap()),
original_size: u64::from_be_bytes(s.data[40..48].try_into().unwrap()),
current_size: u64::from_be_bytes(s.data[48..56].try_into().unwrap()),
disk_geometry: u32::from_be_bytes(s.data[56..60].try_into().unwrap()),
disk_type: u32::from_be_bytes(s.data[60..64].try_into().unwrap()),
checksum: u32::from_be_bytes(s.data[64..68].try_into().unwrap()),
unique_id: u128::from_be_bytes(s.data[68..84].try_into().unwrap()),
saved_state: u8::from_be_bytes(s.data[84..85].try_into().unwrap()),
cookie: u64::from_be_bytes(sector[0..8].try_into().unwrap()),
features: u32::from_be_bytes(sector[8..12].try_into().unwrap()),
file_format_version: u32::from_be_bytes(sector[12..16].try_into().unwrap()),
data_offset: u64::from_be_bytes(sector[16..24].try_into().unwrap()),
time_stamp: u32::from_be_bytes(sector[24..28].try_into().unwrap()),
creator_application: u32::from_be_bytes(sector[28..32].try_into().unwrap()),
creator_version: u32::from_be_bytes(sector[32..36].try_into().unwrap()),
creator_host_os: u32::from_be_bytes(sector[36..40].try_into().unwrap()),
original_size: u64::from_be_bytes(sector[40..48].try_into().unwrap()),
current_size: u64::from_be_bytes(sector[48..56].try_into().unwrap()),
disk_geometry: u32::from_be_bytes(sector[56..60].try_into().unwrap()),
disk_type: u32::from_be_bytes(sector[60..64].try_into().unwrap()),
checksum: u32::from_be_bytes(sector[64..68].try_into().unwrap()),
unique_id: u128::from_be_bytes(sector[68..84].try_into().unwrap()),
saved_state: u8::from_be_bytes(sector[84..85].try_into().unwrap()),
})
}