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 e29c6298ef5c..8cc11b1987ec 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);