Messages in this thread Patch in this message | | | Date | Mon, 26 Mar 2012 19:09:24 +0400 | From | Cyrill Gorcunov <> | Subject | [rfc] fcntl: Add F_GETOWNER_UIDS option |
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Hi guys,
I would like to get opinions on this proposal. What do you think? Is there some security check I'm missing?
--- From: Cyrill Gorcunov <gorcunov@openvz.org> Subject: fcntl: Add F_GETOWNER_UIDS option
When we restore file descriptors we would like them to look exactly as they were at dumping time.
With help of fcntl it's almost possible, the missing snippet is file owners UIDs.
To be able to read their values the F_GETOWNER_UIDS is introduced.
This option is valid iif CONFIG_CHECKPOINT_RESTORE is turned on, otherwise returning -EINVAL.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> --- fs/fcntl.c | 33 +++++++++++++++++++++++++++++++++ include/asm-generic/fcntl.h | 4 ++++ security/selinux/hooks.c | 1 + 3 files changed, 38 insertions(+)
Index: linux-2.6.git/fs/fcntl.c =================================================================== --- linux-2.6.git.orig/fs/fcntl.c +++ linux-2.6.git/fs/fcntl.c @@ -20,6 +20,7 @@ #include <linux/signal.h> #include <linux/rcupdate.h> #include <linux/pid_namespace.h> +#include <linux/user_namespace.h> #include <asm/poll.h> #include <asm/siginfo.h> @@ -340,6 +341,35 @@ static int f_getown_ex(struct file *filp return ret; } +#ifdef CONFIG_CHECKPOINT_RESTORE +static int f_getowner_uids(struct file *filp, unsigned long arg) +{ + struct user_namespace *user_ns = current_user_ns(); + const struct cred *cred = current_cred(); + uid_t * __user dst = (void * __user)arg; + uid_t src[2]; + int err; + + read_lock(&filp->f_owner.lock); + src[0] = filp->f_owner.uid; + src[1] = filp->f_owner.euid; + read_unlock(&filp->f_owner.lock); + + src[0] = user_ns_map_uid(user_ns, cred, src[0]); + src[1] = user_ns_map_uid(user_ns, cred, src[1]); + + err = put_user(src[0], &dst[0]); + err |= put_user(src[1], &dst[1]); + + return err; +} +#else +static int f_getowner_uids(struct file *filp, unsigned long arg) +{ + return -EINVAL; +} +#endif + static long do_fcntl(int fd, unsigned int cmd, unsigned long arg, struct file *filp) { @@ -396,6 +426,9 @@ static long do_fcntl(int fd, unsigned in case F_SETOWN_EX: err = f_setown_ex(filp, arg); break; + case F_GETOWNER_UIDS: + err = f_getowner_uids(filp, arg); + break; case F_GETSIG: err = filp->f_owner.signum; break; Index: linux-2.6.git/include/asm-generic/fcntl.h =================================================================== --- linux-2.6.git.orig/include/asm-generic/fcntl.h +++ linux-2.6.git/include/asm-generic/fcntl.h @@ -120,6 +120,10 @@ #define F_GETOWN_EX 16 #endif +#ifndef F_GETOWNER_UIDS +#define F_GETOWNER_UIDS 17 +#endif + #define F_OWNER_TID 0 #define F_OWNER_PID 1 #define F_OWNER_PGRP 2 Index: linux-2.6.git/security/selinux/hooks.c =================================================================== --- linux-2.6.git.orig/security/selinux/hooks.c +++ linux-2.6.git/security/selinux/hooks.c @@ -3138,6 +3138,7 @@ static int selinux_file_fcntl(struct fil case F_GETFL: case F_GETOWN: case F_GETSIG: + case F_GETOWNER_UIDS: /* Just check FD__USE permission */ err = file_has_perm(cred, file, 0); break;
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