diff options
| -rw-r--r-- | fs/open.c | 37 | ||||
| -rw-r--r-- | include/linux/capability.h | 2 | ||||
| -rw-r--r-- | include/linux/securebits.h | 15 | ||||
| -rw-r--r-- | kernel/capability.c | 21 |
4 files changed, 53 insertions, 22 deletions
@@ -16,6 +16,7 @@ #include <linux/namei.h> #include <linux/backing-dev.h> #include <linux/capability.h> +#include <linux/securebits.h> #include <linux/security.h> #include <linux/mount.h> #include <linux/vfs.h> @@ -425,7 +426,7 @@ asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode) { struct nameidata nd; int old_fsuid, old_fsgid; - kernel_cap_t old_cap; + kernel_cap_t uninitialized_var(old_cap); /* !SECURE_NO_SETUID_FIXUP */ int res; if (mode & ~S_IRWXO) /* where's F_OK, X_OK, W_OK, R_OK? */ @@ -433,23 +434,27 @@ asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode) old_fsuid = current->fsuid; old_fsgid = current->fsgid; - old_cap = current->cap_effective; current->fsuid = current->uid; current->fsgid = current->gid; - /* - * Clear the capabilities if we switch to a non-root user - * - * FIXME: There is a race here against sys_capset. The - * capabilities can change yet we will restore the old - * value below. We should hold task_capabilities_lock, - * but we cannot because user_path_walk can sleep. - */ - if (current->uid) - cap_clear(current->cap_effective); - else - current->cap_effective = current->cap_permitted; + if (!issecure(SECURE_NO_SETUID_FIXUP)) { + /* + * Clear the capabilities if we switch to a non-root user + */ +#ifndef CONFIG_SECURITY_FILE_CAPABILITIES + /* + * FIXME: There is a race here against sys_capset. The + * capabilities can change yet we will restore the old + * value below. We should hold task_capabilities_lock, + * but we cannot because user_path_walk can sleep. + */ +#endif /* ndef CONFIG_SECURITY_FILE_CAPABILITIES */ + if (current->uid) + old_cap = cap_set_effective(__cap_empty_set); + else + old_cap = cap_set_effective(current->cap_permitted); + } res = __user_walk_fd(dfd, filename, LOOKUP_FOLLOW|LOOKUP_ACCESS, &nd); if (res) @@ -478,7 +483,9 @@ out_path_release: out: current->fsuid = old_fsuid; current->fsgid = old_fsgid; - current->cap_effective = old_cap; + + if (!issecure(SECURE_NO_SETUID_FIXUP)) + cap_set_effective(old_cap); return res; } diff --git a/include/linux/capability.h b/include/linux/capability.h index fa830f8..0267384 100644 --- a/include/linux/capability.h +++ b/include/linux/capability.h @@ -501,6 +501,8 @@ extern const kernel_cap_t __cap_empty_set; extern const kernel_cap_t __cap_full_set; extern const kernel_cap_t __cap_init_eff_set; +kernel_cap_t cap_set_effective(const kernel_cap_t pE_new); + int capable(int cap); int __capable(struct task_struct *t, int cap); diff --git a/include/linux/securebits.h b/include/linux/securebits.h index c1f19db..92f09bd 100644 --- a/include/linux/securebits.h +++ b/include/linux/securebits.h @@ -7,14 +7,15 @@ inheritance of root-permissions and suid-root executable under compatibility mode. We raise the effective and inheritable bitmasks *of the executable file* if the effective uid of the new process is - 0. If the real uid is 0, we raise the inheritable bitmask of the + 0. If the real uid is 0, we raise the effective (legacy) bit of the executable file. */ #define SECURE_NOROOT 0 #define SECURE_NOROOT_LOCKED 1 /* make bit-0 immutable */ -/* When set, setuid to/from uid 0 does not trigger capability-"fixes" - to be compatible with old programs relying on set*uid to loose - privileges. When unset, setuid doesn't change privileges. */ +/* When set, setuid to/from uid 0 does not trigger capability-"fixup". + When unset, to provide compatiblility with old programs relying on + set*uid to gain/lose privilege, transitions to/from uid 0 cause + capabilities to be gained/lost. */ #define SECURE_NO_SETUID_FIXUP 2 #define SECURE_NO_SETUID_FIXUP_LOCKED 3 /* make bit-2 immutable */ @@ -26,10 +27,10 @@ #define SECURE_KEEP_CAPS 4 #define SECURE_KEEP_CAPS_LOCKED 5 /* make bit-4 immutable */ -/* Each securesetting is implemented using two bits. One bit specify +/* Each securesetting is implemented using two bits. One bit specifies whether the setting is on or off. The other bit specify whether the - setting is fixed or not. A setting which is fixed cannot be changed - from user-level. */ + setting is locked or not. A setting which is locked cannot be + changed from user-level. */ #define issecure_mask(X) (1 << (X)) #define issecure(X) (issecure_mask(X) & current->securebits) diff --git a/kernel/capability.c b/kernel/capability.c index cfbe442..901e0fd 100644 --- a/kernel/capability.c +++ b/kernel/capability.c @@ -121,6 +121,27 @@ static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy) * uninteresting and/or not to be changed. */ +/* + * Atomically modify the effective capabilities returning the original + * value. No permission check is performed here - it is assumed that the + * caller is permitted to set the desired effective capabilities. + */ +kernel_cap_t cap_set_effective(const kernel_cap_t pE_new) +{ + kernel_cap_t pE_old; + + spin_lock(&task_capability_lock); + + pE_old = current->cap_effective; + current->cap_effective = pE_new; + + spin_unlock(&task_capability_lock); + + return pE_old; +} + +EXPORT_SYMBOL(cap_set_effective); + /** * sys_capget - get the capabilities of a given process. * @header: pointer to struct that contains capability version and |