From: Eric Biggers <ebiggers3@gmail.com>
To: Yunlong Song <yunlong.song@huawei.com>
Cc: jaegeuk@kernel.org, chao@kernel.org, yuchao0@huawei.com,
yunlong.song@icloud.com, miaoxie@huawei.com,
bintian.wang@huawei.com, shengyong1@huawei.com,
heyunlei@huawei.com, linux-f2fs-devel@lists.sourceforge.net,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] f2fs: allocate buffer for decrypting filename to avoid panic
Date: Sat, 24 Feb 2018 10:32:30 -0800 [thread overview]
Message-ID: <20180224183230.GA933@zzz.localdomain> (raw)
In-Reply-To: <1519463698-60555-1-git-send-email-yunlong.song@huawei.com>
Hi Yunlong,
On Sat, Feb 24, 2018 at 05:14:58PM +0800, Yunlong Song wrote:
> In some platforms (such as arm), high memory is used, then the
> decrypting filename will cause panic, the reason see commit
> 569cf1876a32e574ba8a7fb825cd91bafd003882 ("f2fs crypto: allocate buffer
> for decrypting filename"):
>
> We got dentry pages from high_mem, and its address space directly goes into the
> decryption path via f2fs_fname_disk_to_usr.
> But, sg_init_one assumes the address is not from high_mem, so we can get this
> panic since it doesn't call kmap_high but kunmap_high is triggered at the end.
>
> kernel BUG at ../../../../../../kernel/mm/highmem.c:290!
> Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
> ...
> (kunmap_high+0xb0/0xb8) from [<c0114534>] (__kunmap_atomic+0xa0/0xa4)
> (__kunmap_atomic+0xa0/0xa4) from [<c035f028>] (blkcipher_walk_done+0x128/0x1ec)
> (blkcipher_walk_done+0x128/0x1ec) from [<c0366c24>] (crypto_cbc_decrypt+0xc0/0x170)
> (crypto_cbc_decrypt+0xc0/0x170) from [<c0367148>] (crypto_cts_decrypt+0xc0/0x114)
> (crypto_cts_decrypt+0xc0/0x114) from [<c035ea98>] (async_decrypt+0x40/0x48)
> (async_decrypt+0x40/0x48) from [<c032ca34>] (f2fs_fname_disk_to_usr+0x124/0x304)
> (f2fs_fname_disk_to_usr+0x124/0x304) from [<c03056fc>] (f2fs_fill_dentries+0xac/0x188)
> (f2fs_fill_dentries+0xac/0x188) from [<c03059c8>] (f2fs_readdir+0x1f0/0x300)
> (f2fs_readdir+0x1f0/0x300) from [<c0218054>] (vfs_readdir+0x90/0xb4)
> (vfs_readdir+0x90/0xb4) from [<c0218418>] (SyS_getdents64+0x64/0xcc)
> (SyS_getdents64+0x64/0xcc) from [<c0105ba0>] (ret_fast_syscall+0x0/0x30)
>
> Howerver, later patches:
> commit 922ec355f86365388203672119b5bca346a45085 ("f2fs crypto: avoid
> unneeded memory allocation when {en/de}crypting symlink")
> commit e06f86e61d7a67fe6e826010f57aa39c674f4b1b ("f2fs crypto: avoid
> unneeded memory allocation in ->readdir")
>
> reverts the codes, which causes panic again in arm, so let's add the old
> patch again.
>
> Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
> ---
> fs/f2fs/dir.c | 7 +++++++
> fs/f2fs/namei.c | 10 +++++++++-
> 2 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
> index f00b5ed..c0cf3e7b 100644
> --- a/fs/f2fs/dir.c
> +++ b/fs/f2fs/dir.c
> @@ -825,9 +825,16 @@ int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d,
> int save_len = fstr->len;
> int err;
>
> + de_name.name = kmalloc(de_name.len, GFP_NOFS);
> + if (!de_name.name)
> + return -ENOMEM;
> +
> + memcpy(de_name.name, d->filename[bit_pos], de_name.len);
> +
> err = fscrypt_fname_disk_to_usr(d->inode,
> (u32)de->hash_code, 0,
> &de_name, fstr);
> + kfree(de_name.name);
> if (err)
> return err;
>
> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
> index c4c94c7..2cb70c1 100644
> --- a/fs/f2fs/namei.c
> +++ b/fs/f2fs/namei.c
> @@ -1170,8 +1170,13 @@ static const char *f2fs_encrypted_get_link(struct dentry *dentry,
>
> /* Symlink is encrypted */
> sd = (struct fscrypt_symlink_data *)caddr;
> - cstr.name = sd->encrypted_path;
> cstr.len = le16_to_cpu(sd->len);
> + cstr.name = kmalloc(cstr.len, GFP_NOFS);
> + if (!cstr.name) {
> + res = -ENOMEM;
> + goto errout;
> + }
> + memcpy(cstr.name, sd->encrypted_path, cstr.len);
>
> /* this is broken symlink case */
> if (unlikely(cstr.len == 0)) {
> @@ -1198,6 +1203,8 @@ static const char *f2fs_encrypted_get_link(struct dentry *dentry,
> goto errout;
> }
>
> + kfree(cstr.name);
> +
> paddr = pstr.name;
>
> /* Null-terminate the name */
> @@ -1207,6 +1214,7 @@ static const char *f2fs_encrypted_get_link(struct dentry *dentry,
> set_delayed_call(done, kfree_link, paddr);
> return paddr;
> errout:
> + kfree(cstr.name);
> fscrypt_fname_free_buffer(&pstr);
> put_page(cpage);
> return ERR_PTR(res);
> --
> 1.8.5.2
>
The pagecache for symlinks in f2fs already uses lowmem only, so the change to
->get_link() isn't needed. Also that part of the patch doesn't apply to
upstream.
For directories we may need your fix. Note: kmalloc + memcpy should be replaced
with kmemdup. But alternatively, directory pages could be restricted to lowmem
which would match ext4.
Eric
next prev parent reply other threads:[~2018-02-24 18:32 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-24 9:14 [PATCH] f2fs: allocate buffer for decrypting filename to avoid panic Yunlong Song
2018-02-24 18:32 ` Eric Biggers [this message]
2018-02-26 3:06 ` Yunlong Song
2018-02-26 3:42 ` Chao Yu
2018-02-26 2:57 ` [PATCH v2] " Yunlong Song
2018-02-27 10:40 ` Chao Yu
2018-02-28 2:19 ` [PATCH v3] " Yunlong Song
2018-02-28 2:49 ` Chao Yu
2018-02-28 3:17 ` [PATCH v4] Revert "f2fs crypto: avoid unneeded memory allocation in ->readdir" Yunlong Song
2018-02-28 5:48 ` Jaegeuk Kim
2018-02-28 9:50 ` Chao Yu
2018-03-01 2:50 ` Jaegeuk Kim
2018-03-01 3:02 ` Chao Yu
2018-02-28 12:32 ` Yunlong Song
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