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Message-ID: <20121004085750.GA12118@bandura.brq.redhat.com>
Date: Thu, 4 Oct 2012 10:57:50 +0200
From: Anton Arapov <anton@...hat.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
Ananth N Mavinakayanahalli <ananth@...ibm.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/7] uprobes: Fix the racy uprobe->flags manipulation
On Sun, Sep 30, 2012 at 09:42:27PM +0200, Oleg Nesterov wrote:
> Multiple threads can manipulate uprobe->flags, this is obviously
> unsafe. For example mmap can set UPROBE_COPY_INSN while register
> tries to set UPROBE_RUN_HANDLER, the latter can also race with
> can_skip_sstep() which clears UPROBE_SKIP_SSTEP.
>
> Change this code to use bitops.
>
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> ---
> kernel/events/uprobes.c | 28 ++++++++++++++--------------
> 1 files changed, 14 insertions(+), 14 deletions(-)
Re-generating this one because of updated patch 4/7, so that it
will apply cleanly.
Anton
-------------------------------------------------------------------
From: Oleg Nesterov <oleg@...hat.com>
Date: Sun, 30 Sep 2012 21:42:27 +0200
Subject: [PATCH] uprobes: Fix the racy uprobe->flags manipulation
Multiple threads can manipulate uprobe->flags, this is obviously
unsafe. For example mmap can set UPROBE_COPY_INSN while register
tries to set UPROBE_RUN_HANDLER, the latter can also race with
can_skip_sstep() which clears UPROBE_SKIP_SSTEP.
Change this code to use bitops.
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
kernel/events/uprobes.c | 28 ++++++++++++++--------------
1 file changed, 14 insertions(+), 14 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 72067e6..7a8690e 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -79,11 +79,11 @@ static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ];
static atomic_t uprobe_events = ATOMIC_INIT(0);
/* Have a copy of original instruction */
-#define UPROBE_COPY_INSN 0x1
+#define UPROBE_COPY_INSN 0
/* Dont run handlers when first register/ last unregister in progress*/
-#define UPROBE_RUN_HANDLER 0x2
+#define UPROBE_RUN_HANDLER 1
/* Can skip singlestep */
-#define UPROBE_SKIP_SSTEP 0x4
+#define UPROBE_SKIP_SSTEP 2
struct uprobe {
struct rb_node rb_node; /* node in the rb tree */
@@ -94,7 +94,7 @@ struct uprobe {
struct uprobe_consumer *consumers;
struct inode *inode; /* Also hold a ref to inode */
loff_t offset;
- int flags;
+ unsigned long flags;
struct arch_uprobe arch;
};
@@ -423,7 +423,7 @@ static struct uprobe *insert_uprobe(struct uprobe *uprobe)
spin_unlock(&uprobes_treelock);
/* For now assume that the instruction need not be single-stepped */
- uprobe->flags |= UPROBE_SKIP_SSTEP;
+ __set_bit(UPROBE_SKIP_SSTEP, &uprobe->flags);
return u;
}
@@ -466,7 +466,7 @@ static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
{
struct uprobe_consumer *uc;
- if (!(uprobe->flags & UPROBE_RUN_HANDLER))
+ if (!test_bit(UPROBE_RUN_HANDLER, &uprobe->flags))
return;
down_read(&uprobe->consumer_rwsem);
@@ -577,11 +577,11 @@ static int uprobe_copy_insn(struct uprobe *uprobe, struct file *file,
{
int ret = 0;
- if (uprobe->flags & UPROBE_COPY_INSN)
+ if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
return ret;
mutex_lock(&uprobe->copy_mutex);
- if (uprobe->flags & UPROBE_COPY_INSN)
+ if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
goto out;
ret = copy_insn(uprobe, file);
@@ -601,7 +601,7 @@ static int uprobe_copy_insn(struct uprobe *uprobe, struct file *file,
UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
smp_wmb(); /* pairs with rmb() in find_active_uprobe() */
- uprobe->flags |= UPROBE_COPY_INSN;
+ set_bit(UPROBE_COPY_INSN, &uprobe->flags);
ret = 0;
out:
mutex_unlock(&uprobe->copy_mutex);
@@ -852,7 +852,7 @@ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *
uprobe->consumers = NULL;
__uprobe_unregister(uprobe);
} else {
- uprobe->flags |= UPROBE_RUN_HANDLER;
+ set_bit(UPROBE_RUN_HANDLER, &uprobe->flags);
}
}
@@ -885,7 +885,7 @@ void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consume
if (consumer_del(uprobe, uc)) {
if (!uprobe->consumers) {
__uprobe_unregister(uprobe);
- uprobe->flags &= ~UPROBE_RUN_HANDLER;
+ clear_bit(UPROBE_RUN_HANDLER, &uprobe->flags);
}
}
@@ -1346,10 +1346,10 @@ bool uprobe_deny_signal(void)
*/
static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs)
{
- if (uprobe->flags & UPROBE_SKIP_SSTEP) {
+ if (test_bit(UPROBE_SKIP_SSTEP, &uprobe->flags)) {
if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
return true;
- uprobe->flags &= ~UPROBE_SKIP_SSTEP;
+ clear_bit(UPROBE_SKIP_SSTEP, &uprobe->flags);
}
return false;
}
@@ -1428,7 +1428,7 @@ static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
* new and not-yet-analyzed uprobe at the same address, restart.
*/
smp_rmb(); /* pairs with wmb() in install_breakpoint() */
- if (uprobe && unlikely(!(uprobe->flags & UPROBE_COPY_INSN))) {
+ if (uprobe && unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags))) {
put_uprobe(uprobe);
uprobe = NULL;
*is_swbp = 0;
--
1.7.11.7
--
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