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author | David Howells <dhowells@redhat.com> | 2008-08-14 11:37:28 +0100 |
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committer | James Morris <jmorris@namei.org> | 2008-08-14 22:59:43 +1000 |
commit | 5cd9c58fbe9ec92b45b27e131719af4f2bd9eb40 (patch) | |
tree | 8573db001b4dc3c2ad97102dda42b841c40b5f6c /security/smack/smack_lsm.c | |
parent | 8d0968abd03ec6b407df117adc773562386702fa (diff) | |
download | linux-5cd9c58fbe9ec92b45b27e131719af4f2bd9eb40.tar.gz linux-5cd9c58fbe9ec92b45b27e131719af4f2bd9eb40.tar.bz2 linux-5cd9c58fbe9ec92b45b27e131719af4f2bd9eb40.zip |
security: Fix setting of PF_SUPERPRIV by __capable()
Fix the setting of PF_SUPERPRIV by __capable() as it could corrupt the flags
the target process if that is not the current process and it is trying to
change its own flags in a different way at the same time.
__capable() is using neither atomic ops nor locking to protect t->flags. This
patch removes __capable() and introduces has_capability() that doesn't set
PF_SUPERPRIV on the process being queried.
This patch further splits security_ptrace() in two:
(1) security_ptrace_may_access(). This passes judgement on whether one
process may access another only (PTRACE_MODE_ATTACH for ptrace() and
PTRACE_MODE_READ for /proc), and takes a pointer to the child process.
current is the parent.
(2) security_ptrace_traceme(). This passes judgement on PTRACE_TRACEME only,
and takes only a pointer to the parent process. current is the child.
In Smack and commoncap, this uses has_capability() to determine whether
the parent will be permitted to use PTRACE_ATTACH if normal checks fail.
This does not set PF_SUPERPRIV.
Two of the instances of __capable() actually only act on current, and so have
been changed to calls to capable().
Of the places that were using __capable():
(1) The OOM killer calls __capable() thrice when weighing the killability of a
process. All of these now use has_capability().
(2) cap_ptrace() and smack_ptrace() were using __capable() to check to see
whether the parent was allowed to trace any process. As mentioned above,
these have been split. For PTRACE_ATTACH and /proc, capable() is now
used, and for PTRACE_TRACEME, has_capability() is used.
(3) cap_safe_nice() only ever saw current, so now uses capable().
(4) smack_setprocattr() rejected accesses to tasks other than current just
after calling __capable(), so the order of these two tests have been
switched and capable() is used instead.
(5) In smack_file_send_sigiotask(), we need to allow privileged processes to
receive SIGIO on files they're manipulating.
(6) In smack_task_wait(), we let a process wait for a privileged process,
whether or not the process doing the waiting is privileged.
I've tested this with the LTP SELinux and syscalls testscripts.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Andrew G. Morgan <morgan@kernel.org>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: James Morris <jmorris@namei.org>
Diffstat (limited to 'security/smack/smack_lsm.c')
-rw-r--r-- | security/smack/smack_lsm.c | 49 |
1 files changed, 34 insertions, 15 deletions
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 1b40e558f983..87d75417ea93 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -87,27 +87,46 @@ struct inode_smack *new_inode_smack(char *smack) */ /** - * smack_ptrace - Smack approval on ptrace - * @ptp: parent task pointer + * smack_ptrace_may_access - Smack approval on PTRACE_ATTACH * @ctp: child task pointer * * Returns 0 if access is OK, an error code otherwise * * Do the capability checks, and require read and write. */ -static int smack_ptrace(struct task_struct *ptp, struct task_struct *ctp, - unsigned int mode) +static int smack_ptrace_may_access(struct task_struct *ctp, unsigned int mode) { int rc; - rc = cap_ptrace(ptp, ctp, mode); + rc = cap_ptrace_may_access(ctp, mode); if (rc != 0) return rc; - rc = smk_access(ptp->security, ctp->security, MAY_READWRITE); - if (rc != 0 && __capable(ptp, CAP_MAC_OVERRIDE)) + rc = smk_access(current->security, ctp->security, MAY_READWRITE); + if (rc != 0 && capable(CAP_MAC_OVERRIDE)) return 0; + return rc; +} + +/** + * smack_ptrace_traceme - Smack approval on PTRACE_TRACEME + * @ptp: parent task pointer + * + * Returns 0 if access is OK, an error code otherwise + * + * Do the capability checks, and require read and write. + */ +static int smack_ptrace_traceme(struct task_struct *ptp) +{ + int rc; + + rc = cap_ptrace_traceme(ptp); + if (rc != 0) + return rc; + rc = smk_access(ptp->security, current->security, MAY_READWRITE); + if (rc != 0 && has_capability(ptp, CAP_MAC_OVERRIDE)) + return 0; return rc; } @@ -923,7 +942,7 @@ static int smack_file_send_sigiotask(struct task_struct *tsk, */ file = container_of(fown, struct file, f_owner); rc = smk_access(file->f_security, tsk->security, MAY_WRITE); - if (rc != 0 && __capable(tsk, CAP_MAC_OVERRIDE)) + if (rc != 0 && has_capability(tsk, CAP_MAC_OVERRIDE)) return 0; return rc; } @@ -1164,12 +1183,12 @@ static int smack_task_wait(struct task_struct *p) * account for the smack labels having gotten to * be different in the first place. * - * This breaks the strict subjet/object access + * This breaks the strict subject/object access * control ideal, taking the object's privilege * state into account in the decision as well as * the smack value. */ - if (capable(CAP_MAC_OVERRIDE) || __capable(p, CAP_MAC_OVERRIDE)) + if (capable(CAP_MAC_OVERRIDE) || has_capability(p, CAP_MAC_OVERRIDE)) return 0; return rc; @@ -2016,9 +2035,6 @@ static int smack_setprocattr(struct task_struct *p, char *name, { char *newsmack; - if (!__capable(p, CAP_MAC_ADMIN)) - return -EPERM; - /* * Changing another process' Smack value is too dangerous * and supports no sane use case. @@ -2026,6 +2042,9 @@ static int smack_setprocattr(struct task_struct *p, char *name, if (p != current) return -EPERM; + if (!capable(CAP_MAC_ADMIN)) + return -EPERM; + if (value == NULL || size == 0 || size >= SMK_LABELLEN) return -EINVAL; @@ -2552,7 +2571,8 @@ static void smack_release_secctx(char *secdata, u32 seclen) struct security_operations smack_ops = { .name = "smack", - .ptrace = smack_ptrace, + .ptrace_may_access = smack_ptrace_may_access, + .ptrace_traceme = smack_ptrace_traceme, .capget = cap_capget, .capset_check = cap_capset_check, .capset_set = cap_capset_set, @@ -2729,4 +2749,3 @@ static __init int smack_init(void) * all processes and objects when they are created. */ security_initcall(smack_init); - |