From: Minchan Kim <minchan@xxxxxxxxxx> Subject: zram: fix double free backing device If blkdev_get fails, we shouldn't do blkdev_put. Otherwise, kernel emits below log. This patch fixes it. [ 31.073006] WARNING: CPU: 0 PID: 1893 at fs/block_dev.c:1828 blkdev_put+0x105/0x120 [ 31.075104] Modules linked in: [ 31.075898] CPU: 0 PID: 1893 Comm: swapoff Not tainted 4.19.0+ #453 [ 31.077484] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 [ 31.079589] RIP: 0010:blkdev_put+0x105/0x120 [ 31.080606] Code: 48 c7 80 a0 00 00 00 00 00 00 00 48 c7 c7 40 e7 40 96 e8 6e 47 73 00 48 8b bb e0 00 00 00 e9 2c ff ff ff 0f 0b e9 75 ff ff ff <0f> 0b e9 5a ff ff ff 48 c7 80 a0 00 00 00 00 00 00 00 eb 87 0f 1f [ 31.085080] RSP: 0018:ffffb409005c7ed0 EFLAGS: 00010297 [ 31.086383] RAX: ffff9779fe5a8040 RBX: ffff9779fbc17300 RCX: 00000000b9fc37a4 [ 31.088105] RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffffffff9640e740 [ 31.089850] RBP: ffff9779fbc17318 R08: ffffffff95499a89 R09: 0000000000000004 [ 31.091201] R10: ffffb409005c7e50 R11: 7a9ef6088ff4d4a1 R12: 0000000000000083 [ 31.092276] R13: ffff9779fe607b98 R14: 0000000000000000 R15: ffff9779fe607a38 [ 31.093355] FS: 00007fc118d9b840(0000) GS:ffff9779fc600000(0000) knlGS:0000000000000000 [ 31.094582] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 31.095541] CR2: 00007fc11894b8dc CR3: 00000000339f6001 CR4: 0000000000160ef0 [ 31.096781] Call Trace: [ 31.097212] __x64_sys_swapoff+0x46d/0x490 [ 31.097914] do_syscall_64+0x5a/0x190 [ 31.098550] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 31.099402] RIP: 0033:0x7fc11843ec27 [ 31.100013] Code: 73 01 c3 48 8b 0d 71 62 2c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 a8 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 41 62 2c 00 f7 d8 64 89 01 48 [ 31.103149] RSP: 002b:00007ffdf69be648 EFLAGS: 00000206 ORIG_RAX: 00000000000000a8 [ 31.104425] RAX: ffffffffffffffda RBX: 00000000011d98c0 RCX: 00007fc11843ec27 [ 31.105627] RDX: 0000000000000001 RSI: 0000000000000001 RDI: 00000000011d98c0 [ 31.106847] RBP: 0000000000000001 R08: 00007ffdf69be690 R09: 0000000000000001 [ 31.108038] R10: 00000000000002b1 R11: 0000000000000206 R12: 0000000000000001 [ 31.109231] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 31.110433] irq event stamp: 4466 [ 31.111001] hardirqs last enabled at (4465): [<ffffffff953ebd43>] __free_pages_ok+0x1e3/0x490 [ 31.112437] hardirqs last disabled at (4466): [<ffffffff95201b7a>] trace_hardirqs_off_thunk+0x1a/0x1c [ 31.113973] softirqs last enabled at (3420): [<ffffffff95e00333>] __do_softirq+0x333/0x446 [ 31.115364] softirqs last disabled at (3407): [<ffffffff9527aee1>] irq_exit+0xd1/0xe0 Link: http://lkml.kernel.org/r/20181127055429.251614-3-minchan@xxxxxxxxxx Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx> Reviewed-by: Joey Pabalinas <joeypabalinas@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> [4.14+] Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- --- a/drivers/block/zram/zram_drv.c~zram-fix-double-free-backing-device +++ a/drivers/block/zram/zram_drv.c @@ -387,8 +387,10 @@ static ssize_t backing_dev_store(struct bdev = bdgrab(I_BDEV(inode)); err = blkdev_get(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL, zram); - if (err < 0) + if (err < 0) { + bdev = NULL; goto out; + } nr_pages = i_size_read(inode) >> PAGE_SHIFT; bitmap_sz = BITS_TO_LONGS(nr_pages) * sizeof(long); _
