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From: Andy Lutomirski on 26 Mar 2010 09:50
This flag is preserved across execve_nosecurity. It's obviously dangerous, so
we only allow it if PR_RESTRICT_EXEC is set.

Signed-off-by: Andy Lutomirski <luto(a)mit.edu>
---
fs/compat.c | 3 +++
fs/exec.c | 3 +++
include/linux/prctl.h | 5 +++++
include/linux/sched.h | 1 +
kernel/fork.c | 1 +
kernel/sys.c | 13 +++++++++++++
6 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/fs/compat.c b/fs/compat.c
index a091da6..4b7f61f 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1468,6 +1468,9 @@ int compat_do_execve(char * filename,
bool clear_in_exec;
int retval;

+ if (current->force_execve_nosecurity)
+ change_security = false;
+
if (current->restrict_exec && change_security) {
retval = -EPERM;
goto out_ret;
diff --git a/fs/exec.c b/fs/exec.c
index 37fb5fa..0e045b8 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1350,6 +1350,9 @@ int do_execve(char * filename,
bool clear_in_exec;
int retval;

+ if (current->force_execve_nosecurity)
+ change_security = false;
+
if (current->restrict_exec && change_security) {
retval = -EPERM;
goto out_ret;
diff --git a/include/linux/prctl.h b/include/linux/prctl.h
index b926055..8465df3 100644
--- a/include/linux/prctl.h
+++ b/include/linux/prctl.h
@@ -108,4 +108,9 @@

#define PR_GET_RESTRICT 36

+/* Get/set execve -> execve_nosecurity remapping. */
+#define PR_SET_FORCE_EXECVE_NOSECURITY 37
+#define PR_GET_FORCE_EXECVE_NOSECURITY 38
+
+
#endif /* _LINUX_PRCTL_H */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index d1956f7..59f7bcd 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1303,6 +1303,7 @@ struct task_struct {
unsigned sched_reset_on_fork:1;

unsigned restrict_exec:1; /* Process may not call execve. */
+ unsigned force_execve_nosecurity:1; /* execve means execve_nosecurity */

pid_t pid;
pid_t tgid;
diff --git a/kernel/fork.c b/kernel/fork.c
index 8f994e5..d7e1688 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1044,6 +1044,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
goto bad_fork_free;

p->restrict_exec = current->restrict_exec;
+ p->force_execve_nosecurity = current->force_execve_nosecurity;

/*
* If multiple threads are within copy_process(), then this check
diff --git a/kernel/sys.c b/kernel/sys.c
index 3f4aa33..d34daaa 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1609,6 +1609,19 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
if (arg5 && !error)
error = put_user(0, (unsigned long __user *)arg5);
break;
+ case PR_SET_FORCE_EXECVE_NOSECURITY:
+ if (arg3 | arg4 | arg5)
+ return -EINVAL;
+
+ /* Someone braver could remove this check. */
+ if (!current->restrict_exec)
+ return -EPERM;
+
+ current->force_execve_nosecurity = !!arg2;
+ break;
+ case PR_GET_FORCE_EXECVE_NOSECURITY:
+ error = current->force_execve_nosecurity;
+ break;
default:
error = -EINVAL;
break;
--
1.6.6.1

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Prev: [PATCH 1/2] Tools perf builtin-trace.c: #includes cleanup
Next: perf, x86: Add Nehelem PMU programming errata workaround