Re: pkeys on POWER: Access rights not reset on execve

On Mon, May 21, 2018 at 01:29:11PM +0200, Florian Weimer wrote:

On 05/20/2018 09:11 PM, Ram Pai wrote:

quoted

Florian,

Does the following patch fix the problem for you?  Just like x86
I am enabling all keys in the UAMOR register during
initialization itself. Hence any key created by any thread at
any time, will get activated on all threads. So any thread
can change the permission on that key. Smoke tested it
with your test program.

I think this goes in the right direction, but the AMR value after
fork is still strange:

AMR (PID 34912): 0x0000000000000000
AMR after fork (PID 34913): 0x0000000000000000
AMR (PID 34913): 0x0000000000000000
Allocated key in subprocess (PID 34913): 2
Allocated key (PID 34912): 2
Setting AMR: 0xffffffffffffffff
New AMR value (PID 34912): 0x0fffffffffffffff
About to call execl (PID 34912) ...
AMR (PID 34912): 0x0fffffffffffffff
AMR after fork (PID 34914): 0x0000000000000003
AMR (PID 34914): 0x0000000000000003
Allocated key in subprocess (PID 34914): 2
Allocated key (PID 34912): 2
Setting AMR: 0xffffffffffffffff
New AMR value (PID 34912): 0x0fffffffffffffff

I mean this line:

AMR after fork (PID 34914): 0x0000000000000003

Shouldn't it be the same as in the parent process?

Fixed it. Please try this patch. If it all works to your satisfaction, I
will clean it up further and send to Michael Ellermen(ppc maintainer).


commit 51f4208ed5baeab1edb9b0f8b68d7144449b3527
Author: Ram Pai [off-list ref]
Date:   Sun Jun 3 14:44:32 2018 -0500

    Fix for the fork bug.
    
    Signed-off-by: Ram Pai [off-list ref]

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 1237f13..999dd08 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c

@@ -582,6 +582,7 @@ static void save_all(struct task_struct *tsk)
 		__giveup_spe(tsk);
 
 	msr_check_and_clear(msr_all_available);
+	thread_pkey_regs_save(&tsk->thread);
 }
 
 void flush_all_to_thread(struct task_struct *tsk)

diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
index ab4519a..af6aa4a 100644
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c

@@ -294,6 +294,7 @@ void thread_pkey_regs_save(struct thread_struct *thread)
 	 */
 	thread->amr = read_amr();
 	thread->iamr = read_iamr();
+	thread->uamor = read_uamor();
 }
 
 void thread_pkey_regs_restore(struct thread_struct *new_thread,

@@ -315,9 +316,13 @@ void thread_pkey_regs_init(struct thread_struct *thread)
 	if (static_branch_likely(&pkey_disabled))
 		return;
 
-	thread->amr = read_amr() & pkey_amr_mask;
-	thread->iamr = read_iamr() & pkey_iamr_mask;
+	thread->amr = pkey_amr_mask;
+	thread->iamr = pkey_iamr_mask;
 	thread->uamor = pkey_uamor_mask;
+
+	write_uamor(pkey_uamor_mask);
+	write_amr(pkey_amr_mask);
+	write_iamr(pkey_iamr_mask);
 }
 
 static inline bool pkey_allows_readwrite(int pkey)

Thanks,
Florian

-- 
Ram Pai