diff mbox series

[v3,3/6] ptrace: Order and comment PT_flags

Message ID 20211009101444.971532166@infradead.org (mailing list archive)
State Deferred, archived
Headers show
Series Freezer rewrite | expand

Commit Message

Peter Zijlstra Oct. 9, 2021, 10:07 a.m. UTC 
Add a comment to the PT_flags to indicate their actual value, this
makes it easier to see what bits are used and where there might be a
possible hole to use.

Notable PT_SEIZED was placed wrong, also PT_EVENT_FLAG() space seems
ill defined, as written is seems to be meant to cover the entire
PTRACE_O_ range offset by 3 bits, which would then be 3+[0..21],
however PT_SEIZED is in the middle of that.

XXX if at all possible, PT_SEIZED should be moved outside of this
range.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 include/linux/ptrace.h      |   32 +++++++++++++++++---------------
 include/uapi/linux/ptrace.h |    3 +++
 2 files changed, 20 insertions(+), 15 deletions(-)

Comments

Will Deacon Oct. 14, 2021, 9:31 a.m. UTC | #1 
On Sat, Oct 09, 2021 at 12:07:57PM +0200, Peter Zijlstra wrote:
> Add a comment to the PT_flags to indicate their actual value, this
> makes it easier to see what bits are used and where there might be a
> possible hole to use.
> 
> Notable PT_SEIZED was placed wrong, also PT_EVENT_FLAG() space seems
> ill defined, as written is seems to be meant to cover the entire
> PTRACE_O_ range offset by 3 bits, which would then be 3+[0..21],
> however PT_SEIZED is in the middle of that.

Why do you think PT_EVENT_FLAG() should cover all the PTRACE_O_* options?
Just going by the name and current callers, I'd only expect it to cover
the PTRACE_EVENT_* flags, no?

But in any case, having the comments is helpful, so:

Acked-by: Will Deacon <will@kernel.org>

Will
Peter Zijlstra Oct. 14, 2021, 2:27 p.m. UTC | #2 
On Thu, Oct 14, 2021 at 10:31:22AM +0100, Will Deacon wrote:
> On Sat, Oct 09, 2021 at 12:07:57PM +0200, Peter Zijlstra wrote:
> > Add a comment to the PT_flags to indicate their actual value, this
> > makes it easier to see what bits are used and where there might be a
> > possible hole to use.
> > 
> > Notable PT_SEIZED was placed wrong, also PT_EVENT_FLAG() space seems
> > ill defined, as written is seems to be meant to cover the entire
> > PTRACE_O_ range offset by 3 bits, which would then be 3+[0..21],
> > however PT_SEIZED is in the middle of that.
> 
> Why do you think PT_EVENT_FLAG() should cover all the PTRACE_O_* options?
> Just going by the name and current callers, I'd only expect it to cover
> the PTRACE_EVENT_* flags, no?

Because PT_EXITKILL and PT_SUSPEND_SECCOMP are also exposed in that same
mapping.

Ideally we'd change PT_OPT_FLAG_SHIFT to 8 or something and have the
high 24 bits for OPT and then use the low 8 bits for SEIZED and the new
flags.
diff mbox series

Patch

--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -28,30 +28,32 @@  extern int ptrace_access_vm(struct task_
  * flags.  When the a task is stopped the ptracer owns task->ptrace.
  */
 
-#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_PTRACED	0x00000001						// 0x00000001
+#define PT_DTRACE	0x00000002 /* delayed trace (used on m68k, i386) */	// 0x00000002
 
 #define PT_OPT_FLAG_SHIFT	3
 /* PT_TRACE_* event enable flags */
 #define PT_EVENT_FLAG(event)	(1 << (PT_OPT_FLAG_SHIFT + (event)))
-#define PT_TRACESYSGOOD		PT_EVENT_FLAG(0)
-#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)
-#define PT_TRACE_EXEC		PT_EVENT_FLAG(PTRACE_EVENT_EXEC)
-#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_SECCOMP	PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP)
 
-#define PT_EXITKILL		(PTRACE_O_EXITKILL << PT_OPT_FLAG_SHIFT)
-#define PT_SUSPEND_SECCOMP	(PTRACE_O_SUSPEND_SECCOMP << PT_OPT_FLAG_SHIFT)
+#define PT_TRACESYSGOOD		PT_EVENT_FLAG(0)			        // 0x00000008
+#define PT_TRACE_FORK		PT_EVENT_FLAG(PTRACE_EVENT_FORK)	        // 0x00000010
+#define PT_TRACE_VFORK		PT_EVENT_FLAG(PTRACE_EVENT_VFORK)	        // 0x00000020
+#define PT_TRACE_CLONE		PT_EVENT_FLAG(PTRACE_EVENT_CLONE)	        // 0x00000040
+#define PT_TRACE_EXEC		PT_EVENT_FLAG(PTRACE_EVENT_EXEC)	        // 0x00000080
+#define PT_TRACE_VFORK_DONE	PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)	        // 0x00000100
+#define PT_TRACE_EXIT		PT_EVENT_FLAG(PTRACE_EVENT_EXIT)	        // 0x00000200
+#define PT_TRACE_SECCOMP	PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP)	        // 0x00000400
+
+#define PT_SEIZED		0x00010000 /* SEIZE used, enable new behavior */// 0x00010000
+
+#define PT_EXITKILL		(PTRACE_O_EXITKILL << PT_OPT_FLAG_SHIFT)	// 0x00800000
+#define PT_SUSPEND_SECCOMP	(PTRACE_O_SUSPEND_SECCOMP << PT_OPT_FLAG_SHIFT) // 0x01000000
 
 /* single stepping state bits (used on ARM and PA-RISC) */
 #define PT_SINGLESTEP_BIT	31
-#define PT_SINGLESTEP		(1<<PT_SINGLESTEP_BIT)
+#define PT_SINGLESTEP		(1<<PT_SINGLESTEP_BIT)				// 0x80000000
 #define PT_BLOCKSTEP_BIT	30
-#define PT_BLOCKSTEP		(1<<PT_BLOCKSTEP_BIT)
+#define PT_BLOCKSTEP		(1<<PT_BLOCKSTEP_BIT)				// 0x40000000
 
 extern long arch_ptrace(struct task_struct *child, long request,
 			unsigned long addr, unsigned long data);
--- a/include/uapi/linux/ptrace.h
+++ b/include/uapi/linux/ptrace.h
@@ -134,6 +134,7 @@  struct ptrace_rseq_configuration {
 #define PTRACE_EVENT_STOP	128
 
 /* Options set using PTRACE_SETOPTIONS or using PTRACE_SEIZE @data param */
+/* Consider overlap with task->ptrace PT_flags */
 #define PTRACE_O_TRACESYSGOOD	1
 #define PTRACE_O_TRACEFORK	(1 << PTRACE_EVENT_FORK)
 #define PTRACE_O_TRACEVFORK	(1 << PTRACE_EVENT_VFORK)
@@ -143,6 +144,8 @@  struct ptrace_rseq_configuration {
 #define PTRACE_O_TRACEEXIT	(1 << PTRACE_EVENT_EXIT)
 #define PTRACE_O_TRACESECCOMP	(1 << PTRACE_EVENT_SECCOMP)
 
+/* PTRACE_O_SEIZED			(1 << 13) */
+
 /* eventless options */
 #define PTRACE_O_EXITKILL		(1 << 20)
 #define PTRACE_O_SUSPEND_SECCOMP	(1 << 21)