linux-kernel - [GIT] Bug fix for Yama

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Date:	Fri, 17 Aug 2012 20:51:24 +1000 (EST)
From:	James Morris <jmorris@...ei.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>
Subject: [GIT] Bug fix for Yama

Please pull this fix for a deadlock in the Yama LSM.

The following changes since commit d9875690d9b89a866022ff49e3fcea892345ad92:
  Linus Torvalds (1):
        Linux 3.6-rc2

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security.git for-linus

Kees Cook (1):
      Yama: access task_struct->comm directly

 security/yama/yama_lsm.c |   10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

commit 7612bfeecc197bbb6629842b5c6ff1967f0a9b70
Author: Kees Cook <keescook@...omium.org>
Date:   Wed Aug 15 11:41:55 2012 -0700

    Yama: access task_struct->comm directly
    
    The core ptrace access checking routine holds a task lock, and when
    reporting a failure, Yama takes a separate task lock. To avoid a
    potential deadlock with two ptracers taking the opposite locks, do not
    use get_task_comm() and just use ->comm directly since accuracy is not
    important for the report.
    
    Reported-by: Fengguang Wu <fengguang.wu@...el.com>
    Suggested-by: Oleg Nesterov <oleg@...hat.com>
    CC: stable@...r.kernel.org
    Signed-off-by: Kees Cook <keescook@...omium.org>
    Acked-by: John Johansen <john.johansen@...onical.com>
    Signed-off-by: James Morris <james.l.morris@...cle.com>

diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index d51b7c7..0cc99a3 100644
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -279,12 +279,9 @@ static int yama_ptrace_access_check(struct task_struct *child,
 	}
 
 	if (rc) {
-		char name[sizeof(current->comm)];
 		printk_ratelimited(KERN_NOTICE
 			"ptrace of pid %d was attempted by: %s (pid %d)\n",
-			child->pid,
-			get_task_comm(name, current),
-			current->pid);
+			child->pid, current->comm, current->pid);
 	}
 
 	return rc;
@@ -319,12 +316,9 @@ static int yama_ptrace_traceme(struct task_struct *parent)
 	}
 
 	if (rc) {
-		char name[sizeof(current->comm)];
 		printk_ratelimited(KERN_NOTICE
 			"ptraceme of pid %d was attempted by: %s (pid %d)\n",
-			current->pid,
-			get_task_comm(name, parent),
-			parent->pid);
+			current->pid, parent->comm, parent->pid);
 	}
 
 	return rc;
--
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