[PATCH] - Missing check for TIF_WORK if trace/audit enabled

[PATCH] - Missing check for TIF_WORK if trace/audit enabled

[Jack Steiner]

It appears that if trace/audit is enabled, the kernel fails to
check for pending work before returning to user mode. 

	Signed-off-by: Jack Steiner <steiner@sgi.com>


---

Tony / Ken - check this carefully. This is not easy code to understand :-)

I noticed the problem running a signal test that sent SIGUSR2 signals to 
itself. Signals were being dropped. I isolated the problem to an uninitialzed
p6:
	
	ia64_trace_syscall -> work_pending_syscall_end -> work_processed_syscall

work_processed_syscall assumes p6 indicates if the kernel is returning to user mode.
Nothing set p6 for this particular path.



Index: linux/arch/ia64/kernel/entry.S
=================================--- linux.orig/arch/ia64/kernel/entry.S	2006-02-15 12:32:49.836316366 -0600
+++ linux/arch/ia64/kernel/entry.S	2006-02-15 15:09:49.983620290 -0600
@@ -569,6 +569,7 @@ GLOBAL_ENTRY(ia64_trace_syscall)
 .mem.offset 0,0; st8.spill [r2]=r8		// store return value in slot for r8
 .mem.offset 8,0; st8.spill [r3]=r10		// clear error indication in slot for r10
 	br.call.sptk.many rp=syscall_trace_leave // give parent a chance to catch return value
+(pUStk)	cmp.eq.unc p6,p0=r0,r0			// p6 <- pUStk
 .ret3:	br.cond.sptk .work_pending_syscall_end
 
 strace_error:

RE: [PATCH] - Missing check for TIF_WORK if trace/audit enabled

[Chen, Kenneth W]

Jack Steiner wrote on Wednesday, February 15, 2006 1:29 PM
> It appears that if trace/audit is enabled, the kernel fails to
> check for pending work before returning to user mode. 
> 
> Tony / Ken - check this carefully. This is not easy code to understand :-)
> 
> I noticed the problem running a signal test that sent SIGUSR2 signals to 
> itself. Signals were being dropped. I isolated the problem to an uninitialzed
> p6:


Jack, I agree with this fix.  The only request I have is to move the .ret3
label up before cmp inst, so cmp and br end up in the same instruction bundle
instead of two right now.


> Index: linux/arch/ia64/kernel/entry.S
> =================================> --- linux.orig/arch/ia64/kernel/entry.S	2006-02-15 12:32:49.836316366 -0600
> +++ linux/arch/ia64/kernel/entry.S	2006-02-15 15:09:49.983620290 -0600
> @@ -569,6 +569,7 @@ GLOBAL_ENTRY(ia64_trace_syscall)
>  .mem.offset 0,0; st8.spill [r2]=r8		// store return value in slot for r8
>  .mem.offset 8,0; st8.spill [r3]=r10		// clear error indication in slot for r10
>  	br.call.sptk.many rp=syscall_trace_leave // give parent a chance to catch return value
> +(pUStk)	cmp.eq.unc p6,p0=r0,r0			// p6 <- pUStk
>  .ret3:	br.cond.sptk .work_pending_syscall_end
>  
>  strace_error:

Re: [PATCH] - Missing check for TIF_WORK if trace/audit enabled

[Jack Steiner]

It appears that if auditing is enabled, the kernel fails to
check for pending signals before returning to user mode. 

	Signed-off-by: Jack Steiner <steiner@sgi.com>


---

Tony - I think this should go into 2.6.16

Second version. Moved the ".ret" label as suggested by Ken.


I noticed the problem running a signal test that sent SIGUSR2 signals to 
itself. Signals were being dropped. I isolated the problem to an uninitialzed
p6:
	
	ia64_trace_syscall -> work_pending_syscall_end -> work_processed_syscall

work_processed_syscall assumes p6 indicates if the kernel is returning to user mode.
Nothing set p6 for this particular path.



Index: linux/arch/ia64/kernel/entry.S
=================================--- linux.orig/arch/ia64/kernel/entry.S	2006-02-15 12:32:49.836316366 -0600
+++ linux/arch/ia64/kernel/entry.S	2006-02-15 19:35:24.539592133 -0600
@@ -569,7 +569,9 @@ GLOBAL_ENTRY(ia64_trace_syscall)
 .mem.offset 0,0; st8.spill [r2]=r8		// store return value in slot for r8
 .mem.offset 8,0; st8.spill [r3]=r10		// clear error indication in slot for r10
 	br.call.sptk.many rp=syscall_trace_leave // give parent a chance to catch return value
-.ret3:	br.cond.sptk .work_pending_syscall_end
+.ret3:
+(pUStk)	cmp.eq.unc p6,p0=r0,r0			// p6 <- pUStk
+	br.cond.sptk .work_pending_syscall_end
 
 strace_error:
 	ld8 r3=[r2]				// load pt_regs.r8