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Date: Mon, 05 Sep 2011 18:51:03 +0200
From: Denys Vlasenko <dvlasenk@...hat.com>
To: Denys Vlasenko <vda.linux@...glemail.com>
Cc: Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] Fix pollution of task->ptrace if PTRACE_SETOPTIONS
fails.
> A crude patch is below. It rolls points 1-4 from above into a single
> new option, PTRACE_O_TRACESTOP.
For easier review, split it into two parts. Part 1 follows.
(It is still not even compile-tested).
--
vda
Fix pollution of task->ptrace if PTRACE_SETOPTIONS fails.
If PTRACE_SETOPTIONS fails, options should not be affected.
While at it, simplified ptrace_setoptions():
Exchanged PT_TRACESYSGOOD and PT_PTRACE_CAP bit positions, which made
PT_option bits contiguous and therefore made ptrace_setoptions much
simpler.
PT_EVENT_FLAG_SHIFT was not particularly useful, PT_OPT_FLAG_SHIFT with
value of PT_EVENT_FLAG_SHIFT-1 is easier to use.
PT_TRACE_MASK constant is nuked, the only its use is replaced by
(PTRACE_O_MASK << PT_OPT_FLAG_SHIFT).
Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 800f113..9aa669c 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -88,13 +88,12 @@
#define PT_SEIZED 0x00010000 /* SEIZE used, enable new behavior */
#define PT_PTRACED 0x00000001
#define PT_DTRACE 0x00000002 /* delayed trace (used on m68k, i386) */
-#define PT_TRACESYSGOOD 0x00000004
-#define PT_PTRACE_CAP 0x00000008 /* ptracer can follow suid-exec */
+#define PT_PTRACE_CAP 0x00000004 /* ptracer can follow suid-exec */
+#define PT_OPT_FLAG_SHIFT 3
+#define PT_TRACESYSGOOD 0x00000008 /* must be directly before PT_TRACE_event bits! */
/* PT_TRACE_* event enable flags */
-#define PT_EVENT_FLAG_SHIFT 4
-#define PT_EVENT_FLAG(event) (1 << (PT_EVENT_FLAG_SHIFT + (event) - 1))
-
+#define PT_EVENT_FLAG(event) (1 << (PT_OPT_FLAG_SHIFT + (event)))
#define PT_TRACE_FORK PT_EVENT_FLAG(PTRACE_EVENT_FORK)
#define PT_TRACE_VFORK PT_EVENT_FLAG(PTRACE_EVENT_VFORK)
#define PT_TRACE_CLONE PT_EVENT_FLAG(PTRACE_EVENT_CLONE)
@@ -102,8 +101,6 @@
#define PT_TRACE_VFORK_DONE PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)
#define PT_TRACE_EXIT PT_EVENT_FLAG(PTRACE_EVENT_EXIT)
-#define PT_TRACE_MASK 0x000003f4
-
/* single stepping state bits (used on ARM and PA-RISC) */
#define PT_SINGLESTEP_BIT 31
#define PT_SINGLESTEP (1<<PT_SINGLESTEP_BIT)
@@ -228,7 +225,7 @@ static inline void ptrace_init_task(struct task_struct *child, bool ptrace)
child->ptrace = current->ptrace;
__ptrace_link(child, current->parent);
- if (child->ptrace & PT_SEIZED)
+ if (child->ptrace & PTRACE_EVENT_STOP)
task_set_jobctl_pending(child, JOBCTL_TRAP_STOP);
else
sigaddset(&child->pending.signal, SIGSTOP);
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 9de3ecf..9c3536d 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -219,19 +219,23 @@ static int ptrace_attach(struct task_struct *task, long request,
/*
* SEIZE will enable new ptrace behaviors which will be implemented
- * gradually. SEIZE_DEVEL is used to prevent applications
+ * gradually. SEIZE_DEVEL bit is used to prevent applications
* expecting full SEIZE behaviors trapping on kernel commits which
* are still in the process of implementing them.
*
* Only test programs for new ptrace behaviors being implemented
* should set SEIZE_DEVEL. If unset, SEIZE will fail with -EIO.
*
- * Once SEIZE behaviors are completely implemented, this flag and
- * the following test will be removed.
+ * Once SEIZE behaviors are completely implemented, this flag
+ * will be removed.
*/
retval = -EIO;
- if (seize && !(flags & PTRACE_SEIZE_DEVEL))
- goto out;
+ if (seize) {
+ if ((flags & ~(long)PTRACE_O_MASK) != PTRACE_SEIZE_DEVEL)
+ goto out;
+ flags &= ~PTRACE_SEIZE_DEVEL;
+ } else
+ flags = 0;
audit_ptrace(task);
@@ -243,7 +247,7 @@ static int ptrace_attach(struct task_struct *task, long request,
/*
* Protect exec's credential calculations against our interference;
- * interference; SUID, SGID and LSM creds get determined differently
+ * SUID, SGID and LSM creds get determined differently
* under ptrace.
*/
retval = -ERESTARTNOINTR;
@@ -509,30 +513,13 @@ int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long ds
static int ptrace_setoptions(struct task_struct *child, unsigned long data)
{
- child->ptrace &= ~PT_TRACE_MASK;
-
- if (data & PTRACE_O_TRACESYSGOOD)
- child->ptrace |= PT_TRACESYSGOOD;
-
- if (data & PTRACE_O_TRACEFORK)
- child->ptrace |= PT_TRACE_FORK;
-
- if (data & PTRACE_O_TRACEVFORK)
- child->ptrace |= PT_TRACE_VFORK;
-
- if (data & PTRACE_O_TRACECLONE)
- child->ptrace |= PT_TRACE_CLONE;
-
- if (data & PTRACE_O_TRACEEXEC)
- child->ptrace |= PT_TRACE_EXEC;
-
- if (data & PTRACE_O_TRACEVFORKDONE)
- child->ptrace |= PT_TRACE_VFORK_DONE;
+ if (data & ~(long)PTRACE_O_MASK)
+ return -EINVAL;
- if (data & PTRACE_O_TRACEEXIT)
- child->ptrace |= PT_TRACE_EXIT;
+ child->ptrace &= ~(PTRACE_O_MASK << PT_OPT_FLAG_SHIFT);
+ child->ptrace |= (data << PT_OPT_FLAG_SHIFT);
- return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
+ return 0;
}
static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
--
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