2017-09-04 17:50:09

by Colin King

Subject: [PATCH][capabilities-next] commoncap: move assignment of fs_ns to avoid null pointer dereference

From: Colin Ian King <[email protected]>

The pointer fs_ns is assigned from inode->i_ib->s_user_ns before
a null pointer check on inode, hence if inode is actually null we
will get a null pointer dereference on this assignment. Fix this
by only dereferencing inode after the null pointer check on
inode.

Detected by CoverityScan CID#1455328 ("Dereference before null check")

Fixes: 8db6c34f1dbc ("Introduce v3 namespaced file capabilities")
Signed-off-by: Colin Ian King <[email protected]>
---
security/commoncap.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/security/commoncap.c b/security/commoncap.c
index c25e0d27537f..fc46f5b85251 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -585,13 +585,14 @@ int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data
struct vfs_ns_cap_data data, *nscaps = &data;
struct vfs_cap_data *caps = (struct vfs_cap_data *) &data;
kuid_t rootkuid;
- struct user_namespace *fs_ns = inode->i_sb->s_user_ns;
+ struct user_namespace *fs_ns;

memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));

if (!inode)
return -ENODATA;

+ fs_ns = inode->i_sb->s_user_ns;
size = __vfs_getxattr((struct dentry *)dentry, inode,
XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ);
if (size == -ENODATA || size == -EOPNOTSUPP)
--
2.14.1

2017-09-04 18:53:31

by Serge E. Hallyn

Subject: Re: [PATCH][capabilities-next] commoncap: move assignment of fs_ns to avoid null pointer dereference

On Mon, Sep 04, 2017 at 06:50:05PM +0100, Colin King wrote:
> From: Colin Ian King <[email protected]>
>
> The pointer fs_ns is assigned from inode->i_ib->s_user_ns before
> a null pointer check on inode, hence if inode is actually null we
> will get a null pointer dereference on this assignment. Fix this
> by only dereferencing inode after the null pointer check on
> inode.
>
> Detected by CoverityScan CID#1455328 ("Dereference before null check")
>
> Fixes: 8db6c34f1dbc ("Introduce v3 namespaced file capabilities")
> Signed-off-by: Colin Ian King <[email protected]>

thanks!

Acked-by: Serge Hallyn <[email protected]>

> ---
> security/commoncap.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/security/commoncap.c b/security/commoncap.c
> index c25e0d27537f..fc46f5b85251 100644
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -585,13 +585,14 @@ int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data
> struct vfs_ns_cap_data data, *nscaps = &data;
> struct vfs_cap_data *caps = (struct vfs_cap_data *) &data;
> kuid_t rootkuid;
> - struct user_namespace *fs_ns = inode->i_sb->s_user_ns;
> + struct user_namespace *fs_ns;
>
> memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
>
> if (!inode)
> return -ENODATA;
>
> + fs_ns = inode->i_sb->s_user_ns;
> size = __vfs_getxattr((struct dentry *)dentry, inode,
> XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ);
> if (size == -ENODATA || size == -EOPNOTSUPP)
> --
> 2.14.1