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Subject[PATCH 4.15 060/146] bcache: fix crashes in duplicate cache device register
Date
4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tang Junhui <tang.junhui@zte.com.cn>

commit cc40daf91bdddbba72a4a8cd0860640e06668309 upstream.

Kernel crashed when register a duplicate cache device, the call trace is
bellow:
[ 417.643790] CPU: 1 PID: 16886 Comm: bcache-register Tainted: G
W OE 4.15.5-amd64-preempt-sysrq-20171018 #2
[ 417.643861] Hardware name: LENOVO 20ERCTO1WW/20ERCTO1WW, BIOS
N1DET41W (1.15 ) 12/31/2015
[ 417.643870] RIP: 0010:bdevname+0x13/0x1e
[ 417.643876] RSP: 0018:ffffa3aa9138fd38 EFLAGS: 00010282
[ 417.643884] RAX: 0000000000000000 RBX: ffff8c8f2f2f8000 RCX: ffffd6701f8
c7edf
[ 417.643890] RDX: ffffa3aa9138fd88 RSI: ffffa3aa9138fd88 RDI: 00000000000
00000
[ 417.643895] RBP: ffffa3aa9138fde0 R08: ffffa3aa9138fae8 R09: 00000000000
1850e
[ 417.643901] R10: ffff8c8eed34b271 R11: ffff8c8eed34b250 R12: 00000000000
00000
[ 417.643906] R13: ffffd6701f78f940 R14: ffff8c8f38f80000 R15: ffff8c8ea7d
90000
[ 417.643913] FS: 00007fde7e66f500(0000) GS:ffff8c8f61440000(0000) knlGS:
0000000000000000
[ 417.643919] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 417.643925] CR2: 0000000000000314 CR3: 00000007e6fa0001 CR4: 00000000003
606e0
[ 417.643931] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 00000000000
00000
[ 417.643938] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 00000000000
00400
[ 417.643946] Call Trace:
[ 417.643978] register_bcache+0x1117/0x1270 [bcache]
[ 417.643994] ? slab_pre_alloc_hook+0x15/0x3c
[ 417.644001] ? slab_post_alloc_hook.isra.44+0xa/0x1a
[ 417.644013] ? kernfs_fop_write+0xf6/0x138
[ 417.644020] kernfs_fop_write+0xf6/0x138
[ 417.644031] __vfs_write+0x31/0xcc
[ 417.644043] ? current_kernel_time64+0x10/0x36
[ 417.644115] ? __audit_syscall_entry+0xbf/0xe3
[ 417.644124] vfs_write+0xa5/0xe2
[ 417.644133] SyS_write+0x5c/0x9f
[ 417.644144] do_syscall_64+0x72/0x81
[ 417.644161] entry_SYSCALL_64_after_hwframe+0x3d/0xa2
[ 417.644169] RIP: 0033:0x7fde7e1c1974
[ 417.644175] RSP: 002b:00007fff13009a38 EFLAGS: 00000246 ORIG_RAX: 0000000
000000001
[ 417.644183] RAX: ffffffffffffffda RBX: 0000000001658280 RCX: 00007fde7e1c
1974
[ 417.644188] RDX: 000000000000000a RSI: 0000000001658280 RDI: 000000000000
0001
[ 417.644193] RBP: 000000000000000a R08: 0000000000000003 R09: 000000000000
0077
[ 417.644198] R10: 000000000000089e R11: 0000000000000246 R12: 000000000000
0001
[ 417.644203] R13: 000000000000000a R14: 7fffffffffffffff R15: 000000000000
0000
[ 417.644213] Code: c7 c2 83 6f ee 98 be 20 00 00 00 48 89 df e8 6c 27 3b 0
0 48 89 d8 5b c3 0f 1f 44 00 00 48 8b 47 70 48 89 f2 48 8b bf 80 00 00 00 <8
b> b0 14 03 00 00 e9 73 ff ff ff 0f 1f 44 00 00 48 8b 47 40 39
[ 417.644302] RIP: bdevname+0x13/0x1e RSP: ffffa3aa9138fd38
[ 417.644306] CR2: 0000000000000314

When registering duplicate cache device in register_cache(), after failure
on calling register_cache_set(), bch_cache_release() will be called, then
bdev will be freed, so bdevname(bdev, name) caused kernel crash.

Since bch_cache_release() will free bdev, so in this patch we make sure
bdev being freed if register_cache() fail, and do not free bdev again in
register_bcache() when register_cache() fail.

Signed-off-by: Tang Junhui <tang.junhui@zte.com.cn>
Reported-by: Marc MERLIN <marc@merlins.org>
Tested-by: Michael Lyle <mlyle@lyle.org>
Reviewed-by: Michael Lyle <mlyle@lyle.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/bcache/super.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)

--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1191,7 +1191,7 @@ static void register_bdev(struct cache_s

return;
err:
- pr_notice("error opening %s: %s", bdevname(bdev, name), err);
+ pr_notice("error %s: %s", bdevname(bdev, name), err);
bcache_device_stop(&dc->disk);
}

@@ -1859,6 +1859,8 @@ static int register_cache(struct cache_s
const char *err = NULL; /* must be set for any error case */
int ret = 0;

+ bdevname(bdev, name);
+
memcpy(&ca->sb, sb, sizeof(struct cache_sb));
ca->bdev = bdev;
ca->bdev->bd_holder = ca;
@@ -1867,11 +1869,12 @@ static int register_cache(struct cache_s
ca->sb_bio.bi_io_vec[0].bv_page = sb_page;
get_page(sb_page);

- if (blk_queue_discard(bdev_get_queue(ca->bdev)))
+ if (blk_queue_discard(bdev_get_queue(bdev)))
ca->discard = CACHE_DISCARD(&ca->sb);

ret = cache_alloc(ca);
if (ret != 0) {
+ blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
if (ret == -ENOMEM)
err = "cache_alloc(): -ENOMEM";
else
@@ -1894,14 +1897,14 @@ static int register_cache(struct cache_s
goto out;
}

- pr_info("registered cache device %s", bdevname(bdev, name));
+ pr_info("registered cache device %s", name);

out:
kobject_put(&ca->kobj);

err:
if (err)
- pr_notice("error opening %s: %s", bdevname(bdev, name), err);
+ pr_notice("error %s: %s", name, err);

return ret;
}
@@ -1990,6 +1993,7 @@ static ssize_t register_bcache(struct ko
if (err)
goto err_close;

+ err = "failed to register device";
if (SB_IS_BDEV(sb)) {
struct cached_dev *dc = kzalloc(sizeof(*dc), GFP_KERNEL);
if (!dc)
@@ -2004,7 +2008,7 @@ static ssize_t register_bcache(struct ko
goto err_close;

if (register_cache(sb, sb_page, bdev, ca) != 0)
- goto err_close;
+ goto err;
}
out:
if (sb_page)
@@ -2017,7 +2021,7 @@ out:
err_close:
blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
err:
- pr_info("error opening %s: %s", path, err);
+ pr_info("error %s: %s", path, err);
ret = -EINVAL;
goto out;
}

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