From: Seth Forshee <seth.forshee-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> To: "Eric W. Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>, Serge Hallyn <serge.hallyn-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>, James Morris <james.l.morris-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>, "Serge E. Hallyn" <serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org> Cc: linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Miklos Szeredi <mszeredi-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Seth Forshee <seth.forshee-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>, dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, linux-security-module-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-raid-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, fuse-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, Austin S Hemmelgarn <ahferroin7-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, linux-mtd-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Alexander Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>, selinux-+05T5uksL2qpZYMLLGbcSA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Pavel Tikhomirov <ptikhomirov-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org> Subject: [PATCH v4 17/21] capabilities: Allow privileged user in s_user_ns to set security.* xattrs Date: Tue, 26 Apr 2016 14:36:30 -0500 [thread overview] Message-ID: <1461699396-33000-18-git-send-email-seth.forshee@canonical.com> (raw) In-Reply-To: <1461699396-33000-1-git-send-email-seth.forshee-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> A privileged user in s_user_ns will generally have the ability to manipulate the backing store and insert security.* xattrs into the filesystem directly. Therefore the kernel must be prepared to handle these xattrs from unprivileged mounts, and it makes little sense for commoncap to prevent writing these xattrs to the filesystem. The capability and LSM code have already been updated to appropriately handle xattrs from unprivileged mounts, so it is safe to loosen this restriction on setting xattrs. The exception to this logic is that writing xattrs to a mounted filesystem may also cause the LSM inode_post_setxattr or inode_setsecurity callbacks to be invoked. SELinux will deny the xattr update by virtue of applying mountpoint labeling to unprivileged userns mounts, and Smack will deny the writes for any user without global CAP_MAC_ADMIN, so loosening the capability check in commoncap is safe in this respect as well. Signed-off-by: Seth Forshee <seth.forshee-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> Acked-by: Serge Hallyn <serge.hallyn-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> --- security/commoncap.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/security/commoncap.c b/security/commoncap.c index e657227d221e..12477afaa8ed 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -664,15 +664,17 @@ int cap_bprm_secureexec(struct linux_binprm *bprm) int cap_inode_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags) { + struct user_namespace *user_ns = dentry->d_sb->s_user_ns; + if (!strcmp(name, XATTR_NAME_CAPS)) { - if (!capable(CAP_SETFCAP)) + if (!ns_capable(user_ns, CAP_SETFCAP)) return -EPERM; return 0; } if (!strncmp(name, XATTR_SECURITY_PREFIX, sizeof(XATTR_SECURITY_PREFIX) - 1) && - !capable(CAP_SYS_ADMIN)) + !ns_capable(user_ns, CAP_SYS_ADMIN)) return -EPERM; return 0; } @@ -690,15 +692,17 @@ int cap_inode_setxattr(struct dentry *dentry, const char *name, */ int cap_inode_removexattr(struct dentry *dentry, const char *name) { + struct user_namespace *user_ns = dentry->d_sb->s_user_ns; + if (!strcmp(name, XATTR_NAME_CAPS)) { - if (!capable(CAP_SETFCAP)) + if (!ns_capable(user_ns, CAP_SETFCAP)) return -EPERM; return 0; } if (!strncmp(name, XATTR_SECURITY_PREFIX, sizeof(XATTR_SECURITY_PREFIX) - 1) && - !capable(CAP_SYS_ADMIN)) + !ns_capable(user_ns, CAP_SYS_ADMIN)) return -EPERM; return 0; } -- 2.7.4 ------------------------------------------------------------------------------ Find and fix application performance issues faster with Applications Manager Applications Manager provides deep performance insights into multiple tiers of your business applications. It resolves application problems quickly and reduces your MTTR. Get your free trial! https://ad.doubleclick.net/ddm/clk/302982198;130105516;z -- fuse-devel mailing list To unsubscribe or subscribe, visit https://lists.sourceforge.net/lists/listinfo/fuse-devel
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From: Seth Forshee <seth.forshee@canonical.com> To: "Eric W. Biederman" <ebiederm@xmission.com>, Serge Hallyn <serge.hallyn@canonical.com>, James Morris <james.l.morris@oracle.com>, "Serge E. Hallyn" <serge@hallyn.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk>, Richard Weinberger <richard.weinberger@gmail.com>, Austin S Hemmelgarn <ahferroin7@gmail.com>, Miklos Szeredi <mszeredi@redhat.com>, Pavel Tikhomirov <ptikhomirov@virtuozzo.com>, linux-kernel@vger.kernel.org, linux-bcache@vger.kernel.org, dm-devel@redhat.com, linux-raid@vger.kernel.org, linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org, fuse-devel@lists.sourceforge.net, linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov, cgroups@vger.kernel.org, Seth Forshee <seth.forshee@canonical.com> Subject: [PATCH v4 17/21] capabilities: Allow privileged user in s_user_ns to set security.* xattrs Date: Tue, 26 Apr 2016 14:36:30 -0500 [thread overview] Message-ID: <1461699396-33000-18-git-send-email-seth.forshee@canonical.com> (raw) In-Reply-To: <1461699396-33000-1-git-send-email-seth.forshee@canonical.com> A privileged user in s_user_ns will generally have the ability to manipulate the backing store and insert security.* xattrs into the filesystem directly. Therefore the kernel must be prepared to handle these xattrs from unprivileged mounts, and it makes little sense for commoncap to prevent writing these xattrs to the filesystem. The capability and LSM code have already been updated to appropriately handle xattrs from unprivileged mounts, so it is safe to loosen this restriction on setting xattrs. The exception to this logic is that writing xattrs to a mounted filesystem may also cause the LSM inode_post_setxattr or inode_setsecurity callbacks to be invoked. SELinux will deny the xattr update by virtue of applying mountpoint labeling to unprivileged userns mounts, and Smack will deny the writes for any user without global CAP_MAC_ADMIN, so loosening the capability check in commoncap is safe in this respect as well. Signed-off-by: Seth Forshee <seth.forshee@canonical.com> Acked-by: Serge Hallyn <serge.hallyn@canonical.com> --- security/commoncap.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/security/commoncap.c b/security/commoncap.c index e657227d221e..12477afaa8ed 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -664,15 +664,17 @@ int cap_bprm_secureexec(struct linux_binprm *bprm) int cap_inode_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags) { + struct user_namespace *user_ns = dentry->d_sb->s_user_ns; + if (!strcmp(name, XATTR_NAME_CAPS)) { - if (!capable(CAP_SETFCAP)) + if (!ns_capable(user_ns, CAP_SETFCAP)) return -EPERM; return 0; } if (!strncmp(name, XATTR_SECURITY_PREFIX, sizeof(XATTR_SECURITY_PREFIX) - 1) && - !capable(CAP_SYS_ADMIN)) + !ns_capable(user_ns, CAP_SYS_ADMIN)) return -EPERM; return 0; } @@ -690,15 +692,17 @@ int cap_inode_setxattr(struct dentry *dentry, const char *name, */ int cap_inode_removexattr(struct dentry *dentry, const char *name) { + struct user_namespace *user_ns = dentry->d_sb->s_user_ns; + if (!strcmp(name, XATTR_NAME_CAPS)) { - if (!capable(CAP_SETFCAP)) + if (!ns_capable(user_ns, CAP_SETFCAP)) return -EPERM; return 0; } if (!strncmp(name, XATTR_SECURITY_PREFIX, sizeof(XATTR_SECURITY_PREFIX) - 1) && - !capable(CAP_SYS_ADMIN)) + !ns_capable(user_ns, CAP_SYS_ADMIN)) return -EPERM; return 0; } -- 2.7.4
next prev parent reply other threads:[~2016-04-26 19:36 UTC|newest] Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-04-26 19:36 [PATCH v4 00/21] Support fuse mounts in user namespaces Seth Forshee 2016-04-26 19:36 ` Seth Forshee 2016-04-26 19:36 ` [PATCH v4 01/21] fs: fix a posible leak of allocated superblock Seth Forshee 2016-04-26 19:36 ` [PATCH v4 04/21] block_dev: Support checking inode permissions in lookup_bdev() Seth Forshee 2016-04-26 19:36 ` Seth Forshee 2016-04-26 19:36 ` [PATCH v4 05/21] block_dev: Check permissions towards block device inode when mounting Seth Forshee 2016-04-26 19:36 ` [PATCH v4 06/21] fs: Treat foreign mounts as nosuid Seth Forshee 2016-04-26 19:36 ` Seth Forshee 2016-04-26 19:36 ` [PATCH v4 08/21] userns: Replace in_userns with current_in_userns Seth Forshee 2016-04-26 19:36 ` Seth Forshee 2016-04-26 19:36 ` [PATCH v4 09/21] Smack: Handle labels consistently in untrusted mounts Seth Forshee 2016-04-26 19:36 ` [PATCH v4 10/21] fs: Check for invalid i_uid in may_follow_link() Seth Forshee 2016-04-26 19:36 ` Seth Forshee 2016-05-24 15:55 ` Djalal Harouni 2016-04-26 19:36 ` [PATCH v4 11/21] cred: Reject inodes with invalid ids in set_create_file_as() Seth Forshee 2016-04-26 19:36 ` Seth Forshee 2016-04-26 19:36 ` [PATCH v4 15/21] fs: Don't remove suid for CAP_FSETID in s_user_ns Seth Forshee 2016-04-26 19:36 ` Seth Forshee [not found] ` <1461699396-33000-1-git-send-email-seth.forshee-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> 2016-04-26 19:36 ` [PATCH v4 02/21] fs: Remove check of s_user_ns for existing mounts in fs_fully_visible() Seth Forshee 2016-04-26 19:36 ` Seth Forshee 2016-04-26 19:36 ` [PATCH v4 03/21] fs: Allow sysfs and cgroupfs to share super blocks between user namespaces Seth Forshee 2016-04-26 19:36 ` Seth Forshee 2016-04-26 19:36 ` [PATCH v4 07/21] selinux: Add support for unprivileged mounts from " Seth Forshee 2016-04-26 19:36 ` Seth Forshee 2016-04-26 19:36 ` [PATCH v4 12/21] fs: Refuse uid/gid changes which don't map into s_user_ns Seth Forshee 2016-04-26 19:36 ` Seth Forshee 2016-04-26 19:36 ` [PATCH v4 13/21] fs: Update posix_acl support to handle user namespace mounts Seth Forshee 2016-04-26 19:36 ` Seth Forshee 2016-04-26 19:36 ` [PATCH v4 14/21] fs: Allow superblock owner to change ownership of inodes with unmappable ids Seth Forshee 2016-04-26 19:36 ` Seth Forshee 2016-04-26 19:36 ` [PATCH v4 16/21] fs: Allow superblock owner to access do_remount_sb() Seth Forshee 2016-04-26 19:36 ` Seth Forshee 2016-04-26 19:36 ` Seth Forshee [this message] 2016-04-26 19:36 ` [PATCH v4 17/21] capabilities: Allow privileged user in s_user_ns to set security.* xattrs Seth Forshee [not found] ` <1461699396-33000-18-git-send-email-seth.forshee-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> 2016-04-27 7:22 ` James Morris 2016-04-27 7:22 ` James Morris 2016-04-26 19:36 ` [PATCH v4 18/21] fuse: Add support for pid namespaces Seth Forshee 2016-04-26 19:36 ` Seth Forshee 2016-07-20 2:44 ` Sheng Yang [not found] ` <CA+2rt426_pshAauQizcxkfAq16vmEpB4sJ4genW_ucosH3j=zQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2016-07-20 12:52 ` Seth Forshee 2016-07-20 12:52 ` Seth Forshee 2016-07-20 22:28 ` Sheng Yang 2016-07-21 7:25 ` Miklos Szeredi 2016-07-21 7:25 ` Miklos Szeredi 2016-04-26 19:36 ` [PATCH v4 19/21] fuse: Support fuse filesystems outside of init_user_ns Seth Forshee 2016-04-26 19:36 ` Seth Forshee 2016-04-26 19:36 ` [PATCH v4 20/21] fuse: Restrict allow_other to the superblock's namespace or a descendant Seth Forshee 2016-04-26 19:36 ` [PATCH v4 21/21] fuse: Allow user namespace mounts Seth Forshee
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