Re: [PATCH] btrfs: free checksum hash on in close_ctree

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

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On 2019/7/11 下午11:23, Johannes Thumshirn wrote:
> fs_info::csum_hash gets initialized in btrfs_init_csum_hash() which is
> called by open_ctree().
> 
> But it only gets freed if open_ctree() fails, not on normal operation.
> 
> This leads to a memory leak like the following found by kmemleak:
> unreferenced object 0xffff888132cb8720 (size 96):
>   comm "mount", pid 450, jiffies 4294912436 (age 17.584s)
>   hex dump (first 32 bytes):
>     04 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<000000000c9643d4>] crypto_create_tfm+0x2d/0xd0
>     [<00000000ae577f68>] crypto_alloc_tfm+0x4b/0xb0
>     [<000000002b5cdf30>] open_ctree+0xb84/0x2060 [btrfs]
>     [<0000000043204297>] btrfs_mount_root+0x552/0x640 [btrfs]
>     [<00000000c99b10ea>] legacy_get_tree+0x22/0x40
>     [<0000000071a6495f>] vfs_get_tree+0x1f/0xc0
>     [<00000000f180080e>] fc_mount+0x9/0x30
>     [<000000009e36cebd>] vfs_kern_mount.part.11+0x6a/0x80
>     [<0000000004594c05>] btrfs_mount+0x174/0x910 [btrfs]
>     [<00000000c99b10ea>] legacy_get_tree+0x22/0x40
>     [<0000000071a6495f>] vfs_get_tree+0x1f/0xc0
>     [<00000000b86e92c5>] do_mount+0x6b0/0x940
>     [<0000000097464494>] ksys_mount+0x7b/0xd0
>     [<0000000057213c80>] __x64_sys_mount+0x1c/0x20
>     [<00000000cb689b5e>] do_syscall_64+0x43/0x130
>     [<000000002194e289>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Free fs_info::csum_hash in close_ctree() to avoid the memory leak.
> 
> Fixes: 6d97c6e31b55 ("btrfs: add boilerplate code for directly including the crypto framework")

Not yet in upstream, thus I believe David could just fold this fix into
the original commit.

> Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>

Reviewed-by: Qu Wenruo <wqu@suse.com>

Although for the folding case, that reviewed-by won't make much sense.

Thanks,
Qu

> ---
>  fs/btrfs/disk-io.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 41a2bd2e0c56..5f7ee70b3d1a 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -4106,6 +4106,7 @@ void close_ctree(struct btrfs_fs_info *fs_info)
>  	percpu_counter_destroy(&fs_info->dev_replace.bio_counter);
>  	cleanup_srcu_struct(&fs_info->subvol_srcu);
>  
> +	btrfs_free_csum_hash(fs_info);
>  	btrfs_free_stripe_hash_table(fs_info);
>  	btrfs_free_ref_cache(fs_info);
>  }
> 


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