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    Subject[PATCH 5.17 092/772] md/bitmap: dont set sb values if cant pass sanity check
    Date
    From: Heming Zhao <heming.zhao@suse.com>

    [ Upstream commit e68cb83a57a458b01c9739e2ad9cb70b04d1e6d2 ]

    If bitmap area contains invalid data, kernel will crash then mdadm
    triggers "Segmentation fault".
    This is cluster-md speical bug. In non-clustered env, mdadm will
    handle broken metadata case. In clustered array, only kernel space
    handles bitmap slot info. But even this bug only happened in clustered
    env, current sanity check is wrong, the code should be changed.

    How to trigger: (faulty injection)

    dd if=/dev/zero bs=1M count=1 oflag=direct of=/dev/sda
    dd if=/dev/zero bs=1M count=1 oflag=direct of=/dev/sdb
    mdadm -C /dev/md0 -b clustered -e 1.2 -n 2 -l mirror /dev/sda /dev/sdb
    mdadm -Ss
    echo aaa > magic.txt
    == below modifying slot 2 bitmap data ==
    dd if=magic.txt of=/dev/sda seek=16384 bs=1 count=3 <== destroy magic
    dd if=/dev/zero of=/dev/sda seek=16436 bs=1 count=4 <== ZERO chunksize
    mdadm -A /dev/md0 /dev/sda /dev/sdb
    == kernel crashes. mdadm outputs "Segmentation fault" ==

    Reason of kernel crash:

    In md_bitmap_read_sb (called by md_bitmap_create), bad bitmap magic didn't
    block chunksize assignment, and zero value made DIV_ROUND_UP_SECTOR_T()
    trigger "divide error".

    Crash log:

    kernel: md: md0 stopped.
    kernel: md/raid1:md0: not clean -- starting background reconstruction
    kernel: md/raid1:md0: active with 2 out of 2 mirrors
    kernel: dlm: ... ...
    kernel: md-cluster: Joined cluster 44810aba-38bb-e6b8-daca-bc97a0b254aa slot 1
    kernel: md0: invalid bitmap file superblock: bad magic
    kernel: md_bitmap_copy_from_slot can't get bitmap from slot 2
    kernel: md-cluster: Could not gather bitmaps from slot 2
    kernel: divide error: 0000 [#1] SMP NOPTI
    kernel: CPU: 0 PID: 1603 Comm: mdadm Not tainted 5.14.6-1-default
    kernel: Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
    kernel: RIP: 0010:md_bitmap_create+0x1d1/0x850 [md_mod]
    kernel: RSP: 0018:ffffc22ac0843ba0 EFLAGS: 00010246
    kernel: ... ...
    kernel: Call Trace:
    kernel: ? dlm_lock_sync+0xd0/0xd0 [md_cluster 77fe..7a0]
    kernel: md_bitmap_copy_from_slot+0x2c/0x290 [md_mod 24ea..d3a]
    kernel: load_bitmaps+0xec/0x210 [md_cluster 77fe..7a0]
    kernel: md_bitmap_load+0x81/0x1e0 [md_mod 24ea..d3a]
    kernel: do_md_run+0x30/0x100 [md_mod 24ea..d3a]
    kernel: md_ioctl+0x1290/0x15a0 [md_mod 24ea....d3a]
    kernel: ? mddev_unlock+0xaa/0x130 [md_mod 24ea..d3a]
    kernel: ? blkdev_ioctl+0xb1/0x2b0
    kernel: block_ioctl+0x3b/0x40
    kernel: __x64_sys_ioctl+0x7f/0xb0
    kernel: do_syscall_64+0x59/0x80
    kernel: ? exit_to_user_mode_prepare+0x1ab/0x230
    kernel: ? syscall_exit_to_user_mode+0x18/0x40
    kernel: ? do_syscall_64+0x69/0x80
    kernel: entry_SYSCALL_64_after_hwframe+0x44/0xae
    kernel: RIP: 0033:0x7f4a15fa722b
    kernel: ... ...
    kernel: ---[ end trace 8afa7612f559c868 ]---
    kernel: RIP: 0010:md_bitmap_create+0x1d1/0x850 [md_mod]

    Reported-by: kernel test robot <lkp@intel.com>
    Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
    Acked-by: Guoqing Jiang <guoqing.jiang@linux.dev>
    Signed-off-by: Heming Zhao <heming.zhao@suse.com>
    Signed-off-by: Song Liu <song@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/md/md-bitmap.c | 44 ++++++++++++++++++++++--------------------
    1 file changed, 23 insertions(+), 21 deletions(-)

    diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
    index bfd6026d7809..612460d2bdaf 100644
    --- a/drivers/md/md-bitmap.c
    +++ b/drivers/md/md-bitmap.c
    @@ -639,14 +639,6 @@ static int md_bitmap_read_sb(struct bitmap *bitmap)
    daemon_sleep = le32_to_cpu(sb->daemon_sleep) * HZ;
    write_behind = le32_to_cpu(sb->write_behind);
    sectors_reserved = le32_to_cpu(sb->sectors_reserved);
    - /* Setup nodes/clustername only if bitmap version is
    - * cluster-compatible
    - */
    - if (sb->version == cpu_to_le32(BITMAP_MAJOR_CLUSTERED)) {
    - nodes = le32_to_cpu(sb->nodes);
    - strlcpy(bitmap->mddev->bitmap_info.cluster_name,
    - sb->cluster_name, 64);
    - }

    /* verify that the bitmap-specific fields are valid */
    if (sb->magic != cpu_to_le32(BITMAP_MAGIC))
    @@ -668,6 +660,16 @@ static int md_bitmap_read_sb(struct bitmap *bitmap)
    goto out;
    }

    + /*
    + * Setup nodes/clustername only if bitmap version is
    + * cluster-compatible
    + */
    + if (sb->version == cpu_to_le32(BITMAP_MAJOR_CLUSTERED)) {
    + nodes = le32_to_cpu(sb->nodes);
    + strlcpy(bitmap->mddev->bitmap_info.cluster_name,
    + sb->cluster_name, 64);
    + }
    +
    /* keep the array size field of the bitmap superblock up to date */
    sb->sync_size = cpu_to_le64(bitmap->mddev->resync_max_sectors);

    @@ -700,9 +702,9 @@ static int md_bitmap_read_sb(struct bitmap *bitmap)

    out:
    kunmap_atomic(sb);
    - /* Assigning chunksize is required for "re_read" */
    - bitmap->mddev->bitmap_info.chunksize = chunksize;
    if (err == 0 && nodes && (bitmap->cluster_slot < 0)) {
    + /* Assigning chunksize is required for "re_read" */
    + bitmap->mddev->bitmap_info.chunksize = chunksize;
    err = md_setup_cluster(bitmap->mddev, nodes);
    if (err) {
    pr_warn("%s: Could not setup cluster service (%d)\n",
    @@ -713,18 +715,18 @@ static int md_bitmap_read_sb(struct bitmap *bitmap)
    goto re_read;
    }

    -
    out_no_sb:
    - if (test_bit(BITMAP_STALE, &bitmap->flags))
    - bitmap->events_cleared = bitmap->mddev->events;
    - bitmap->mddev->bitmap_info.chunksize = chunksize;
    - bitmap->mddev->bitmap_info.daemon_sleep = daemon_sleep;
    - bitmap->mddev->bitmap_info.max_write_behind = write_behind;
    - bitmap->mddev->bitmap_info.nodes = nodes;
    - if (bitmap->mddev->bitmap_info.space == 0 ||
    - bitmap->mddev->bitmap_info.space > sectors_reserved)
    - bitmap->mddev->bitmap_info.space = sectors_reserved;
    - if (err) {
    + if (err == 0) {
    + if (test_bit(BITMAP_STALE, &bitmap->flags))
    + bitmap->events_cleared = bitmap->mddev->events;
    + bitmap->mddev->bitmap_info.chunksize = chunksize;
    + bitmap->mddev->bitmap_info.daemon_sleep = daemon_sleep;
    + bitmap->mddev->bitmap_info.max_write_behind = write_behind;
    + bitmap->mddev->bitmap_info.nodes = nodes;
    + if (bitmap->mddev->bitmap_info.space == 0 ||
    + bitmap->mddev->bitmap_info.space > sectors_reserved)
    + bitmap->mddev->bitmap_info.space = sectors_reserved;
    + } else {
    md_bitmap_print_sb(bitmap);
    if (bitmap->cluster_slot < 0)
    md_cluster_stop(bitmap->mddev);
    --
    2.35.1


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