[PATCH] ecryptfs: fix kernel panic with null dev_name

[PATCH] ecryptfs: fix kernel panic with null dev_name

[Jeffrey Mitchell]

When mounting eCryptfs, a null "dev_name" argument to ecryptfs_mount()
causes a kernel panic if the parsed options are valid. The easiest way to
reproduce this is to call mount() from userspace with an existing
eCryptfs mount's options and a "source" argument of 0.

Error out if "dev_name" is null in ecryptfs_mount()

Signed-off-by: Jeffrey Mitchell <jeffrey.mitchell@starlab.io>
---
 fs/ecryptfs/main.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index e63259fdef28..b2f6a1937d23 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -492,6 +492,12 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags
 		goto out;
 	}
 
+	if (!dev_name) {
+		rc = -EINVAL;
+		err = "Device name cannot be null";
+		goto out;
+	}
+
 	rc = ecryptfs_parse_options(sbi, raw_data, &check_ruid);
 	if (rc) {
 		err = "Error parsing options";
-- 
2.25.1

Re: [PATCH] ecryptfs: fix kernel panic with null dev_name

[Tyler Hicks]

On 2021-02-26 15:00:23, Jeffrey Mitchell wrote:
> When mounting eCryptfs, a null "dev_name" argument to ecryptfs_mount()
> causes a kernel panic if the parsed options are valid. The easiest way to
> reproduce this is to call mount() from userspace with an existing
> eCryptfs mount's options and a "source" argument of 0.
> 
> Error out if "dev_name" is null in ecryptfs_mount()
> 
> Signed-off-by: Jeffrey Mitchell <jeffrey.mitchell@starlab.io>

Thanks for the fix! I reproduced this on a 4.15 and, while I didn't try
anything older than that, I think it affects the first kernel release
with eCryptfs. I've added the following Fixes tag:

 Fixes: 237fead61998 ("[PATCH] ecryptfs: fs/Makefile and fs/Kconfig")

I've pushed it to the next branch of tyhicks/ecryptfs.git.

Tyler

> ---
>  fs/ecryptfs/main.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
> index e63259fdef28..b2f6a1937d23 100644
> --- a/fs/ecryptfs/main.c
> +++ b/fs/ecryptfs/main.c
> @@ -492,6 +492,12 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags
>  		goto out;
>  	}
>  
> +	if (!dev_name) {
> +		rc = -EINVAL;
> +		err = "Device name cannot be null";
> +		goto out;
> +	}
> +
>  	rc = ecryptfs_parse_options(sbi, raw_data, &check_ruid);
>  	if (rc) {
>  		err = "Error parsing options";
> -- 
> 2.25.1
>