From eb3a72921c8276bf2cd028a458bb83435f16c91c Mon Sep 17 00:00:00 2001
From: Keshavamurthy Anil S <anil.s.keshavamurthy@intel.com>
Date: Wed, 11 Jan 2006 12:17:42 -0800
Subject: [PATCH] [PATCH] kprobes: fix race in recovery of reentrant probe
There is a window where a probe gets removed right after the probe is hit
on some different cpu. In this case probe handlers can't find a matching
probe instance related to break address. In this case we need to read the
original instruction at break address to see if that is not a break/int3
instruction and recover safely.
Previous code had a bug where we were not checking for the above race in
case of reentrant probes and the below patch fixes this race.
Tested on IA64, Powerpc, x86_64.
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
arch/i386/kernel/kprobes.c | 13 +++++++++++++
arch/ia64/kernel/kprobes.c | 7 +++++++
arch/powerpc/kernel/kprobes.c | 12 ++++++++++++
arch/sparc64/kernel/kprobes.c | 8 ++++++++
arch/x86_64/kernel/kprobes.c | 9 +++++++++
5 files changed, 49 insertions(+)
diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index 2f372dbd34fd..6483eeb1a4e8 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -188,6 +188,19 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
kcb->kprobe_status = KPROBE_REENTER;
return 1;
} else {
+ if (regs->eflags & VM_MASK) {
+ /* We are in virtual-8086 mode. Return 0 */
+ goto no_kprobe;
+ }
+ if (*addr != BREAKPOINT_INSTRUCTION) {
+ /* The breakpoint instruction was removed by
+ * another cpu right after we hit, no further
+ * handling of this interrupt is appropriate
+ */
+ regs->eip -= sizeof(kprobe_opcode_t);
+ ret = 1;
+ goto no_kprobe;
+ }
p = __get_cpu_var(current_kprobe);
if (p->break_handler && p->break_handler(p, regs)) {
goto ss_probe;
diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 4de7f6759093..346fedf9ea47 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -638,6 +638,13 @@ static int __kprobes pre_kprobes_handler(struct die_args *args)
if (p->break_handler && p->break_handler(p, regs)) {
goto ss_probe;
}
+ } else if (!is_ia64_break_inst(regs)) {
+ /* The breakpoint instruction was removed by
+ * another cpu right after we hit, no further
+ * handling of this interrupt is appropriate
+ */
+ ret = 1;
+ goto no_kprobe;
} else {
/* Not our break */
goto no_kprobe;
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 27b0c40601fb..cfab48566db1 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -179,6 +179,18 @@ static inline int kprobe_handler(struct pt_regs *regs)
kcb->kprobe_status = KPROBE_REENTER;
return 1;
} else {
+ if (*addr != BREAKPOINT_INSTRUCTION) {
+ /* If trap variant, then it belongs not to us */
+ kprobe_opcode_t cur_insn = *addr;
+ if (is_trap(cur_insn))
+ goto no_kprobe;
+ /* The breakpoint instruction was removed by
+ * another cpu right after we hit, no further
+ * handling of this interrupt is appropriate
+ */
+ ret = 1;
+ goto no_kprobe;
+ }
p = __get_cpu_var(current_kprobe);
if (p->break_handler && p->break_handler(p, regs)) {
goto ss_probe;
diff --git a/arch/sparc64/kernel/kprobes.c b/arch/sparc64/kernel/kprobes.c
index ff5e9d5cad50..b9a9ce70e55c 100644
--- a/arch/sparc64/kernel/kprobes.c
+++ b/arch/sparc64/kernel/kprobes.c
@@ -135,6 +135,14 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
prepare_singlestep(p, regs, kcb);
return 1;
} else {
+ if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
+ /* The breakpoint instruction was removed by
+ * another cpu right after we hit, no further
+ * handling of this interrupt is appropriate
+ */
+ ret = 1;
+ goto no_kprobe;
+ }
p = __get_cpu_var(current_kprobe);
if (p->break_handler && p->break_handler(p, regs))
goto ss_probe;
diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
index b7dc1f816d13..8b866a8572cf 100644
--- a/arch/x86_64/kernel/kprobes.c
+++ b/arch/x86_64/kernel/kprobes.c
@@ -334,6 +334,15 @@ int __kprobes kprobe_handler(struct pt_regs *regs)
return 1;
}
} else {
+ if (*addr != BREAKPOINT_INSTRUCTION) {
+ /* The breakpoint instruction was removed by
+ * another cpu right after we hit, no further
+ * handling of this interrupt is appropriate
+ */
+ regs->rip = (unsigned long)addr;
+ ret = 1;
+ goto no_kprobe;
+ }
p = __get_cpu_var(current_kprobe);
if (p->break_handler && p->break_handler(p, regs)) {
goto ss_probe;
--
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