RE: [f2fs-dev] [PATCH 1/3] f2fs: early check broken symlink length in the encrypted case

[Chao Yu]

Hi Jaegeuk,

> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk@xxxxxxxxxx]
> Sent: Tuesday, December 29, 2015 7:32 AM
> To: linux-kernel@xxxxxxxxxxxxxxx; linux-fsdevel@xxxxxxxxxxxxxxx;
> linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx
> Cc: Jaegeuk Kim
> Subject: [f2fs-dev] [PATCH 1/3] f2fs: early check broken symlink length in the encrypted case
> 
> If link is broken, its len is zero, and we don't need to move forward.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> ---
>  fs/f2fs/namei.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
> index fb41c80..5cc4128 100644
> --- a/fs/f2fs/namei.c
> +++ b/fs/f2fs/namei.c
> @@ -931,7 +931,7 @@ static const char *f2fs_encrypted_follow_link(struct dentry *dentry, void
> **cook
>  {
>  	struct page *cpage = NULL;
>  	char *caddr, *paddr = NULL;
> -	struct f2fs_str cstr;
> +	struct f2fs_str cstr = FSTR_INIT(NULL, 0);
>  	struct f2fs_str pstr = FSTR_INIT(NULL, 0);
>  	struct inode *inode = d_inode(dentry);
>  	struct f2fs_encrypted_symlink_data *sd;
> @@ -952,6 +952,12 @@ static const char *f2fs_encrypted_follow_link(struct dentry *dentry, void
> **cook
>  	/* Symlink is encrypted */
>  	sd = (struct f2fs_encrypted_symlink_data *)caddr;
>  	cstr.len = le16_to_cpu(sd->len);
> +
> +	/* this is broken symlink case */
> +	if (cstr.len == 0) {

This case seems rare, can we add unlikely here?

> +		res = -ENOENT;
> +		goto errout;
> +	}
>  	cstr.name = kmalloc(cstr.len, GFP_NOFS);
>  	if (!cstr.name) {
>  		res = -ENOMEM;
> @@ -960,7 +966,7 @@ static const char *f2fs_encrypted_follow_link(struct dentry *dentry, void
> **cook
>  	memcpy(cstr.name, sd->encrypted_path, cstr.len);
> 
>  	/* this is broken symlink case */
> -	if (cstr.name[0] == 0 && cstr.len == 0) {
> +	if (cstr.name[0] == 0) {

ditto.

Thanks,

>  		res = -ENOENT;
>  		goto errout;
>  	}
> --
> 2.5.4 (Apple Git-61)
> 
> 
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