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81409e5e48
linux-next/fs/ext4/mmp.c
Jason A. Donenfeld d247aabd39 treewide: use get_random_u32_{above,below}() instead of manual loop 
These cases were done with this Coccinelle:

@@
expression E;
identifier I;
@@
-   do {
      ... when != I
-     I = get_random_u32();
      ... when != I
-   } while (I > E);
+   I = get_random_u32_below(E + 1);

@@
expression E;
identifier I;
@@
-   do {
      ... when != I
-     I = get_random_u32();
      ... when != I
-   } while (I >= E);
+   I = get_random_u32_below(E);

@@
expression E;
identifier I;
@@
-   do {
      ... when != I
-     I = get_random_u32();
      ... when != I
-   } while (I < E);
+   I = get_random_u32_above(E - 1);

@@
expression E;
identifier I;
@@
-   do {
      ... when != I
-     I = get_random_u32();
      ... when != I
-   } while (I <= E);
+   I = get_random_u32_above(E);

@@
identifier I;
@@
-   do {
      ... when != I
-     I = get_random_u32();
      ... when != I
-   } while (!I);
+   I = get_random_u32_above(0);

@@
identifier I;
@@
-   do {
      ... when != I
-     I = get_random_u32();
      ... when != I
-   } while (I == 0);
+   I = get_random_u32_above(0);

@@
expression E;
@@
- E + 1 + get_random_u32_below(U32_MAX - E)
+ get_random_u32_above(E)

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2022-11-18 02:15:22 +01:00

390 lines
9.9 KiB
C
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// SPDX-License-Identifier: GPL-2.0
#include <linux/fs.h>
#include <linux/random.h>
#include <linux/buffer_head.h>
#include <linux/utsname.h>
#include <linux/kthread.h>
#include "ext4.h"
/* Checksumming functions */
static __le32 ext4_mmp_csum(struct super_block *sb, struct mmp_struct *mmp)
{
struct ext4_sb_info *sbi = EXT4_SB(sb);
int offset = offsetof(struct mmp_struct, mmp_checksum);
__u32 csum;
csum = ext4_chksum(sbi, sbi->s_csum_seed, (char *)mmp, offset);
return cpu_to_le32(csum);
}
static int ext4_mmp_csum_verify(struct super_block *sb, struct mmp_struct *mmp)
{
if (!ext4_has_metadata_csum(sb))
return 1;
return mmp->mmp_checksum == ext4_mmp_csum(sb, mmp);
}
static void ext4_mmp_csum_set(struct super_block *sb, struct mmp_struct *mmp)
{
if (!ext4_has_metadata_csum(sb))
return;
mmp->mmp_checksum = ext4_mmp_csum(sb, mmp);
}
/*
* Write the MMP block using REQ_SYNC to try to get the block on-disk
* faster.
*/
static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
{
struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data);
/*
* We protect against freezing so that we don't create dirty buffers
* on frozen filesystem.
*/
sb_start_write(sb);
ext4_mmp_csum_set(sb, mmp);
lock_buffer(bh);
bh->b_end_io = end_buffer_write_sync;
get_bh(bh);
submit_bh(REQ_OP_WRITE | REQ_SYNC | REQ_META | REQ_PRIO, bh);
wait_on_buffer(bh);
sb_end_write(sb);
if (unlikely(!buffer_uptodate(bh)))
return -EIO;
return 0;
}
/*
* Read the MMP block. It _must_ be read from disk and hence we clear the
* uptodate flag on the buffer.
*/
static int read_mmp_block(struct super_block *sb, struct buffer_head **bh,
ext4_fsblk_t mmp_block)
{
struct mmp_struct *mmp;
int ret;
if (*bh)
clear_buffer_uptodate(*bh);
/* This would be sb_bread(sb, mmp_block), except we need to be sure
* that the MD RAID device cache has been bypassed, and that the read
* is not blocked in the elevator. */
if (!*bh) {
*bh = sb_getblk(sb, mmp_block);
if (!*bh) {
ret = -ENOMEM;
goto warn_exit;
}
}
lock_buffer(*bh);
ret = ext4_read_bh(*bh, REQ_META | REQ_PRIO, NULL);
if (ret)
goto warn_exit;
mmp = (struct mmp_struct *)((*bh)->b_data);
if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC) {
ret = -EFSCORRUPTED;
goto warn_exit;
}
if (!ext4_mmp_csum_verify(sb, mmp)) {
ret = -EFSBADCRC;
goto warn_exit;
}
return 0;
warn_exit:
brelse(*bh);
*bh = NULL;
ext4_warning(sb, "Error %d while reading MMP block %llu",
ret, mmp_block);
return ret;
}
/*
* Dump as much information as possible to help the admin.
*/
void __dump_mmp_msg(struct super_block *sb, struct mmp_struct *mmp,
const char *function, unsigned int line, const char *msg)
{
__ext4_warning(sb, function, line, "%s", msg);
__ext4_warning(sb, function, line,
"MMP failure info: last update time: %llu, last update node: %.*s, last update device: %.*s",
(unsigned long long)le64_to_cpu(mmp->mmp_time),
(int)sizeof(mmp->mmp_nodename), mmp->mmp_nodename,
(int)sizeof(mmp->mmp_bdevname), mmp->mmp_bdevname);
}
/*
* kmmpd will update the MMP sequence every s_mmp_update_interval seconds
*/
static int kmmpd(void *data)
{
struct super_block *sb = data;
struct ext4_super_block *es = EXT4_SB(sb)->s_es;
struct buffer_head *bh = EXT4_SB(sb)->s_mmp_bh;
struct mmp_struct *mmp;
ext4_fsblk_t mmp_block;
u32 seq = 0;
unsigned long failed_writes = 0;
int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval);
unsigned mmp_check_interval;
unsigned long last_update_time;
unsigned long diff;
int retval = 0;
mmp_block = le64_to_cpu(es->s_mmp_block);
mmp = (struct mmp_struct *)(bh->b_data);
mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds());
/*
* Start with the higher mmp_check_interval and reduce it if
* the MMP block is being updated on time.
*/
mmp_check_interval = max(EXT4_MMP_CHECK_MULT * mmp_update_interval,
EXT4_MMP_MIN_CHECK_INTERVAL);
mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
memcpy(mmp->mmp_nodename, init_utsname()->nodename,
sizeof(mmp->mmp_nodename));
while (!kthread_should_stop() && !sb_rdonly(sb)) {
if (!ext4_has_feature_mmp(sb)) {
ext4_warning(sb, "kmmpd being stopped since MMP feature"
" has been disabled.");
goto wait_to_exit;
}
if (++seq > EXT4_MMP_SEQ_MAX)
seq = 1;
mmp->mmp_seq = cpu_to_le32(seq);
mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds());
last_update_time = jiffies;
retval = write_mmp_block(sb, bh);
/*
* Don't spew too many error messages. Print one every
* (s_mmp_update_interval * 60) seconds.
*/
if (retval) {
if ((failed_writes % 60) == 0) {
ext4_error_err(sb, -retval,
"Error writing to MMP block");
}
failed_writes++;
}
diff = jiffies - last_update_time;
if (diff < mmp_update_interval * HZ)
schedule_timeout_interruptible(mmp_update_interval *
HZ - diff);
/*
* We need to make sure that more than mmp_check_interval
* seconds have not passed since writing. If that has happened
* we need to check if the MMP block is as we left it.
*/
diff = jiffies - last_update_time;
if (diff > mmp_check_interval * HZ) {
struct buffer_head *bh_check = NULL;
struct mmp_struct *mmp_check;
retval = read_mmp_block(sb, &bh_check, mmp_block);
if (retval) {
ext4_error_err(sb, -retval,
"error reading MMP data: %d",
retval);
goto wait_to_exit;
}
mmp_check = (struct mmp_struct *)(bh_check->b_data);
if (mmp->mmp_seq != mmp_check->mmp_seq ||
memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename,
sizeof(mmp->mmp_nodename))) {
dump_mmp_msg(sb, mmp_check,
"Error while updating MMP info. "
"The filesystem seems to have been"
" multiply mounted.");
ext4_error_err(sb, EBUSY, "abort");
put_bh(bh_check);
retval = -EBUSY;
goto wait_to_exit;
}
put_bh(bh_check);
}
/*
* Adjust the mmp_check_interval depending on how much time
* it took for the MMP block to be written.
*/
mmp_check_interval = max(min(EXT4_MMP_CHECK_MULT * diff / HZ,
EXT4_MMP_MAX_CHECK_INTERVAL),
EXT4_MMP_MIN_CHECK_INTERVAL);
mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
}
/*
* Unmount seems to be clean.
*/
mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN);
mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds());
retval = write_mmp_block(sb, bh);
wait_to_exit:
while (!kthread_should_stop()) {
set_current_state(TASK_INTERRUPTIBLE);
if (!kthread_should_stop())
schedule();
}
set_current_state(TASK_RUNNING);
return retval;
}
void ext4_stop_mmpd(struct ext4_sb_info *sbi)
{
if (sbi->s_mmp_tsk) {
kthread_stop(sbi->s_mmp_tsk);
brelse(sbi->s_mmp_bh);
sbi->s_mmp_tsk = NULL;
}
}
/*
* Get a random new sequence number but make sure it is not greater than
* EXT4_MMP_SEQ_MAX.
*/
static unsigned int mmp_new_seq(void)
{
return get_random_u32_below(EXT4_MMP_SEQ_MAX + 1);
}
/*
* Protect the filesystem from being mounted more than once.
*/
int ext4_multi_mount_protect(struct super_block *sb,
ext4_fsblk_t mmp_block)
{
struct ext4_super_block *es = EXT4_SB(sb)->s_es;
struct buffer_head *bh = NULL;
struct mmp_struct *mmp = NULL;
u32 seq;
unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval);
unsigned int wait_time = 0;
int retval;
if (mmp_block < le32_to_cpu(es->s_first_data_block) ||
mmp_block >= ext4_blocks_count(es)) {
ext4_warning(sb, "Invalid MMP block in superblock");
goto failed;
}
retval = read_mmp_block(sb, &bh, mmp_block);
if (retval)
goto failed;
mmp = (struct mmp_struct *)(bh->b_data);
if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
/*
* If check_interval in MMP block is larger, use that instead of
* update_interval from the superblock.
*/
if (le16_to_cpu(mmp->mmp_check_interval) > mmp_check_interval)
mmp_check_interval = le16_to_cpu(mmp->mmp_check_interval);
seq = le32_to_cpu(mmp->mmp_seq);
if (seq == EXT4_MMP_SEQ_CLEAN)
goto skip;
if (seq == EXT4_MMP_SEQ_FSCK) {
dump_mmp_msg(sb, mmp, "fsck is running on the filesystem");
goto failed;
}
wait_time = min(mmp_check_interval * 2 + 1,
mmp_check_interval + 60);
/* Print MMP interval if more than 20 secs. */
if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4)
ext4_warning(sb, "MMP interval %u higher than expected, please"
" wait.\n", wait_time * 2);
if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
ext4_warning(sb, "MMP startup interrupted, failing mount\n");
goto failed;
}
retval = read_mmp_block(sb, &bh, mmp_block);
if (retval)
goto failed;
mmp = (struct mmp_struct *)(bh->b_data);
if (seq != le32_to_cpu(mmp->mmp_seq)) {
dump_mmp_msg(sb, mmp,
"Device is already active on another node.");
goto failed;
}
skip:
/*
* write a new random sequence number.
*/
seq = mmp_new_seq();
mmp->mmp_seq = cpu_to_le32(seq);
retval = write_mmp_block(sb, bh);
if (retval)
goto failed;
/*
* wait for MMP interval and check mmp_seq.
*/
if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
ext4_warning(sb, "MMP startup interrupted, failing mount");
goto failed;
}
retval = read_mmp_block(sb, &bh, mmp_block);
if (retval)
goto failed;
mmp = (struct mmp_struct *)(bh->b_data);
if (seq != le32_to_cpu(mmp->mmp_seq)) {
dump_mmp_msg(sb, mmp,
"Device is already active on another node.");
goto failed;
}
EXT4_SB(sb)->s_mmp_bh = bh;
BUILD_BUG_ON(sizeof(mmp->mmp_bdevname) < BDEVNAME_SIZE);
snprintf(mmp->mmp_bdevname, sizeof(mmp->mmp_bdevname),
"%pg", bh->b_bdev);
/*
* Start a kernel thread to update the MMP block periodically.
*/
EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, sb, "kmmpd-%.*s",
(int)sizeof(mmp->mmp_bdevname),
mmp->mmp_bdevname);
if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
EXT4_SB(sb)->s_mmp_tsk = NULL;
ext4_warning(sb, "Unable to create kmmpd thread for %s.",
sb->s_id);
goto failed;
}
return 0;
failed:
brelse(bh);
return 1;
}
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