On 06/26, Benjamin Herrenschmidt wrote:
>
> On Wed, 2013-06-26 at 16:56 +1000, Stephen Rothwell wrote:
> > Today's linux-next merge of the akpm tree got a conflict in
> > arch/powerpc/kernel/ptrace.c between commit b0b0aa9c7faf
> > ("powerpc/hw_brk: Fix setting of length for exact mode breakpoints") from
> > the powerpc tree and commit "ptrace/powerpc: revert "hw_breakpoints: Fix
> > racy access to ptrace breakpoints"" from the akpm tree.
> >
> > I fixed it up (see below) and can carry the fix as necessary (no action
> > is required).
>
> Where does the latter come from ?
ptrace-powerpc-revert-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints.patch
attached below.
You were cc'ed every time ;)
> Why didn't it go through the powerpc tree ?
Because this series needs to update any user of ptrace_get/put_breakpoints
in arch/ (simply remove these calls), then change the core kernel code, then
fix arch/86.
------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: ptrace/powerpc: revert "hw_breakpoints: Fix racy access to ptrace breakpoints"
This reverts commit 07fa7a0a8a586 ("hw_breakpoints: Fix racy access to
ptrace breakpoints") and removes ptrace_get/put_breakpoints() added by
other commits.
The patch was fine but we can no longer race with SIGKILL after 9899d11f
("ptrace: ensure arch_ptrace/ptrace_request can never race with SIGKILL"),
the __TASK_TRACED tracee can't be woken up and ->ptrace_bps[] can't go
away.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: Michael Neuling <mikey@xxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jan Kratochvil <jan.kratochvil@xxxxxxxxxx>
Cc: Paul Mundt <lethal@xxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Prasad <prasad@xxxxxxxxxxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/ptrace.c | 20 --------------------
1 file changed, 20 deletions(-)
diff -puN arch/powerpc/kernel/ptrace.c~ptrace-powerpc-revert-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints arch/powerpc/kernel/ptrace.c
--- a/arch/powerpc/kernel/ptrace.c~ptrace-powerpc-revert-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints
+++ a/arch/powerpc/kernel/ptrace.c
@@ -974,16 +974,12 @@ int ptrace_set_debugreg(struct task_stru
hw_brk.type = (data & HW_BRK_TYPE_DABR) | HW_BRK_TYPE_PRIV_ALL;
hw_brk.len = 8;
#ifdef CONFIG_HAVE_HW_BREAKPOINT
- if (ptrace_get_breakpoints(task) < 0)
- return -ESRCH;
-
bp = thread->ptrace_bps[0];
if ((!data) || !(hw_brk.type & HW_BRK_TYPE_RDWR)) {
if (bp) {
unregister_hw_breakpoint(bp);
thread->ptrace_bps[0] = NULL;
}
- ptrace_put_breakpoints(task);
return 0;
}
if (bp) {
@@ -996,11 +992,9 @@ int ptrace_set_debugreg(struct task_stru
ret = modify_user_hw_breakpoint(bp, &attr);
if (ret) {
- ptrace_put_breakpoints(task);
return ret;
}
thread->ptrace_bps[0] = bp;
- ptrace_put_breakpoints(task);
thread->hw_brk = hw_brk;
return 0;
}
@@ -1015,12 +1009,9 @@ int ptrace_set_debugreg(struct task_stru
ptrace_triggered, NULL, task);
if (IS_ERR(bp)) {
thread->ptrace_bps[0] = NULL;
- ptrace_put_breakpoints(task);
return PTR_ERR(bp);
}
- ptrace_put_breakpoints(task);
-
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
task->thread.hw_brk = hw_brk;
#else /* CONFIG_PPC_ADV_DEBUG_REGS */
@@ -1439,9 +1430,6 @@ static long ppc_set_hwdebug(struct task_
if (bp_info->trigger_type & PPC_BREAKPOINT_TRIGGER_WRITE)
brk.type |= HW_BRK_TYPE_WRITE;
#ifdef CONFIG_HAVE_HW_BREAKPOINT
- if (ptrace_get_breakpoints(child) < 0)
- return -ESRCH;
-
/*
* Check if the request is for 'range' breakpoints. We can
* support it if range < 8 bytes.
@@ -1449,12 +1437,10 @@ static long ppc_set_hwdebug(struct task_
if (bp_info->addr_mode == PPC_BREAKPOINT_MODE_RANGE_INCLUSIVE) {
len = bp_info->addr2 - bp_info->addr;
} else if (bp_info->addr_mode != PPC_BREAKPOINT_MODE_EXACT) {
- ptrace_put_breakpoints(child);
return -EINVAL;
}
bp = thread->ptrace_bps[0];
if (bp) {
- ptrace_put_breakpoints(child);
return -ENOSPC;
}
@@ -1468,11 +1454,9 @@ static long ppc_set_hwdebug(struct task_
ptrace_triggered, NULL, child);
if (IS_ERR(bp)) {
thread->ptrace_bps[0] = NULL;
- ptrace_put_breakpoints(child);
return PTR_ERR(bp);
}
- ptrace_put_breakpoints(child);
return 1;
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
@@ -1516,16 +1500,12 @@ static long ppc_del_hwdebug(struct task_
return -EINVAL;
#ifdef CONFIG_HAVE_HW_BREAKPOINT
- if (ptrace_get_breakpoints(child) < 0)
- return -ESRCH;
-
bp = thread->ptrace_bps[0];
if (bp) {
unregister_hw_breakpoint(bp);
thread->ptrace_bps[0] = NULL;
} else
ret = -ENOENT;
- ptrace_put_breakpoints(child);
return ret;
#else /* CONFIG_HAVE_HW_BREAKPOINT */
if (child->thread.hw_brk.address == 0)
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
posix_cpu_timer-consolidate-expiry-time-type.patch
posix_cpu_timers-consolidate-timer-list-cleanups.patch
posix_cpu_timers-consolidate-expired-timers-check.patch
posix-timers-correctly-get-dying-task-time-sample-in-posix_cpu_timer_schedule.patch
posix_timers-fix-racy-timer-delta-caching-on-task-exit.patch
lockdep-introduce-lock_acquire_exclusive-shared-helper-macros.patch
lglock-update-lockdep-annotations-to-report-recursive-local-locks.patch
autofs4-allow-autofs-to-work-outside-the-initial-pid-namespace.patch
autofs4-translate-pids-to-the-right-namespace-for-the-daemon.patch
ptrace-x86-revert-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints.patch
ptrace-powerpc-revert-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints.patch
ptrace-arm-revert-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints.patch
ptrace-sh-revert-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints.patch
ptrace-revert-prepare-to-fix-racy-accesses-on-task-breakpoints.patch
ptrace-x86-simplify-the-disable-logic-in-ptrace_write_dr7.patch
ptrace-x86-dont-delay-disable-till-second-pass-in-ptrace_write_dr7.patch
ptrace-x86-introduce-ptrace_register_breakpoint.patch
ptrace-x86-ptrace_write_dr7-should-create-bp-if-disabled.patch
ptrace-x86-cleanup-ptrace_set_debugreg.patch
ptrace-ptrace_detach-should-do-flush_ptrace_hw_breakpointchild.patch
ptrace-x86-flush_ptrace_hw_breakpoint-shoule-clear-the-virtual-debug-registers.patch
x86-kill-tif_debug.patch
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