From e7c5afa30425cef05b4654589cd0056185891a1a Mon Sep 17 00:00:00 2001 From: Vivek Goyal Date: Wed, 13 Jul 2016 10:44:49 -0400 Subject: [PATCH] security,overlayfs: Provide security hook for copy up of xattrs for overlay file Provide a security hook which is called when xattrs of a file are being copied up. This hook is called once for each xattr and LSM can return 0 if the security module wants the xattr to be copied up, 1 if the security module wants the xattr to be discarded on the copy, -EOPNOTSUPP if the security module does not handle/manage the xattr, or a -errno upon an error. Signed-off-by: David Howells Signed-off-by: Vivek Goyal Acked-by: Stephen Smalley [PM: whitespace cleanup for checkpatch.pl] Signed-off-by: Paul Moore Orabug: 25684456 (backport upstream commit 121ab822ef21914adac2fa3730efeeb8fd762473) Signed-off-by: Anand Jain Acked-by: James Morris Reviewed-by: James Morris conflict fix include/linux/security.h security/capability.c security/security.c --- fs/overlayfs/copy_up.c | 7 +++++++ include/linux/security.h | 15 +++++++++++++++ security/capability.c | 6 ++++++ security/security.c | 8 +++++++- 4 files changed, 35 insertions(+), 1 deletion(-) diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c index 2f149dc68e01..4d23335e334d 100644 --- a/fs/overlayfs/copy_up.c +++ b/fs/overlayfs/copy_up.c @@ -71,6 +71,13 @@ retry: goto retry; } + error = security_inode_copy_up_xattr(name); + if (error < 0 && error != -EOPNOTSUPP) + break; + if (error == 1) { + error = 0; + continue; /* Discard */ + } error = vfs_setxattr(new, name, value, size, 0); if (error) break; diff --git a/include/linux/security.h b/include/linux/security.h index 3a32ec884ba2..215313e70591 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -571,6 +571,14 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts) * @src indicates the union dentry of file that is being copied up. * @new pointer to pointer to return newly allocated creds. * Returns 0 on success or a negative error code on error. + * @inode_copy_up_xattr: + * Filter the xattrs being copied up when a unioned file is copied + * up from a lower layer to the union/overlay layer. + * @name indicates the name of the xattr. + * Returns 0 to accept the xattr, 1 to discard the xattr, -EOPNOTSUPP if + * security module does not know about attribute or a negative error code + * to abort the copy up. Note that the caller is responsible for reading + * and writing the xattrs as this hook is merely a filter. * * Security hooks for file operations * @@ -1580,6 +1588,7 @@ struct security_operations { int (*inode_listsecurity) (struct inode *inode, char *buffer, size_t buffer_size); void (*inode_getsecid) (const struct inode *inode, u32 *secid); int (*inode_copy_up)(struct dentry *src, struct cred **new); + int (*inode_copy_up_xattr)(const char *name); int (*file_permission) (struct file *file, int mask); int (*file_alloc_security) (struct file *file); @@ -1867,6 +1876,7 @@ int security_inode_setsecurity(struct inode *inode, const char *name, const void int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size); void security_inode_getsecid(const struct inode *inode, u32 *secid); int security_inode_copy_up(struct dentry *src, struct cred **new); +int security_inode_copy_up_xattr(const char *name); int security_file_permission(struct file *file, int mask); int security_file_alloc(struct file *file); void security_file_free(struct file *file); @@ -2336,6 +2346,11 @@ static inline int security_inode_copy_up(struct dentry *src, struct cred **new) return 0; } +static inline int security_inode_copy_up_xattr(const char *name) +{ + return -EOPNOTSUPP; +} + static inline int security_file_permission(struct file *file, int mask) { return 0; diff --git a/security/capability.c b/security/capability.c index 359fd2f30130..1241a77cc66e 100644 --- a/security/capability.c +++ b/security/capability.c @@ -273,6 +273,11 @@ static int cap_inode_copy_up(struct dentry *src, struct cred **new) return 0; } +static int cap_inode_copy_up_xattr(const char *name) +{ + return -EOPNOTSUPP; +} + #ifdef CONFIG_SECURITY_PATH static int cap_path_mknod(struct path *dir, struct dentry *dentry, umode_t mode, unsigned int dev) @@ -1014,6 +1019,7 @@ void __init security_fixup_ops(struct security_operations *ops) set_to_cap_if_null(ops, inode_listsecurity); set_to_cap_if_null(ops, inode_getsecid); set_to_cap_if_null(ops, inode_copy_up); + set_to_cap_if_null(ops, inode_copy_up_xattr); #ifdef CONFIG_SECURITY_PATH set_to_cap_if_null(ops, path_mknod); set_to_cap_if_null(ops, path_mkdir); diff --git a/security/security.c b/security/security.c index 85bf122235dc..3b5faf7460a1 100644 --- a/security/security.c +++ b/security/security.c @@ -708,10 +708,16 @@ void security_inode_getsecid(const struct inode *inode, u32 *secid) int security_inode_copy_up(struct dentry *src, struct cred **new) { - security_ops->inode_copy_up(src, new); + return security_ops->inode_copy_up(src, new); } EXPORT_SYMBOL(security_inode_copy_up); +int security_inode_copy_up_xattr(const char *name) +{ + return security_ops->inode_copy_up_xattr(name); +} +EXPORT_SYMBOL(security_inode_copy_up_xattr); + int security_file_permission(struct file *file, int mask) { int ret; -- 2.50.1