Fixed optkprobe issues, mainly related to the x86 architecture.
Yang Jihong (2):
x86/kprobes: Fix __recover_optprobed_insn check optimizing logic
x86/kprobes: Fix arch_check_optimized_kprobe check within
optimized_kprobe range
arch/x86/kernel/kprobes/opt.c | 6 +++---
include/linux/kprobes.h | 2 ++
kernel/kprobes.c | 4 ++--
3 files changed, 7 insertions(+), 5 deletions(-)
--
Changes since v1:
- Remove patch1 since there is already a fix patch.
- Add "cc stable" and modify comment for patch2.
- Use "kprobe_disarmed" instead of "kprobe_disabled" for patch3.
- Add fix commmit and "cc stable" for patch3.
2.30.GIT
Since the following commit:
commit f66c0447cca1 ("kprobes: Set unoptimized flag after unoptimizing code")
modified the update timing of the KPROBE_FLAG_OPTIMIZED, a optimized_kprobe
may be in the optimizing or unoptimizing state when op.kp->flags
has KPROBE_FLAG_OPTIMIZED and op->list is not empty.
The __recover_optprobed_insn check logic is incorrect, a kprobe in the
unoptimizing state may be incorrectly determined as unoptimizing.
As a result, incorrect instructions are copied.
The optprobe_queued_unopt function needs to be exported for invoking in
arch directory.
Cc: [email protected]
Fixes: f66c0447cca1 ("kprobes: Set unoptimized flag after unoptimizing code")
Signed-off-by: Yang Jihong <[email protected]>
---
arch/x86/kernel/kprobes/opt.c | 4 ++--
include/linux/kprobes.h | 1 +
kernel/kprobes.c | 2 +-
3 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index e57e07b0edb6..f406bfa9a8cd 100644
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -46,8 +46,8 @@ unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr)
/* This function only handles jump-optimized kprobe */
if (kp && kprobe_optimized(kp)) {
op = container_of(kp, struct optimized_kprobe, kp);
- /* If op->list is not empty, op is under optimizing */
- if (list_empty(&op->list))
+ /* If op is optimized or under unoptimizing */
+ if (list_empty(&op->list) || optprobe_queued_unopt(op))
goto found;
}
}
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index a0b92be98984..ab39285f71a6 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -378,6 +378,7 @@ extern void opt_pre_handler(struct kprobe *p, struct pt_regs *regs);
DEFINE_INSN_CACHE_OPS(optinsn);
extern void wait_for_kprobe_optimizer(void);
+bool optprobe_queued_unopt(struct optimized_kprobe *op);
#else /* !CONFIG_OPTPROBES */
static inline void wait_for_kprobe_optimizer(void) { }
#endif /* CONFIG_OPTPROBES */
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 1c18ecf9f98b..90b0fac6efa0 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -662,7 +662,7 @@ void wait_for_kprobe_optimizer(void)
mutex_unlock(&kprobe_mutex);
}
-static bool optprobe_queued_unopt(struct optimized_kprobe *op)
+bool optprobe_queued_unopt(struct optimized_kprobe *op)
{
struct optimized_kprobe *_op;
--
2.30.GIT
When arch_prepare_optimized_kprobe calculating jump destination address,
it copies original instructions from jmp-optimized kprobe (see
__recover_optprobed_insn), and calculated based on length of original
instruction.
arch_check_optimized_kprobe does not check KPROBE_FLAG_OPTIMATED when
checking whether jmp-optimized kprobe exists.
As a result, setup_detour_execution may jump to a range that has been
overwritten by jump destination address, resulting in an inval opcode error.
For example, assume that register two kprobes whose addresses are
<func+9> and <func+11> in "func" function.
The original code of "func" function is as follows:
0xffffffff816cb5e9 <+9>: push %r12
0xffffffff816cb5eb <+11>: xor %r12d,%r12d
0xffffffff816cb5ee <+14>: test %rdi,%rdi
0xffffffff816cb5f1 <+17>: setne %r12b
0xffffffff816cb5f5 <+21>: push %rbp
1.Register the kprobe for <func+11>, assume that is kp1, corresponding optimized_kprobe is op1.
After the optimization, "func" code changes to:
0xffffffff816cc079 <+9>: push %r12
0xffffffff816cc07b <+11>: jmp 0xffffffffa0210000
0xffffffff816cc080 <+16>: incl 0xf(%rcx)
0xffffffff816cc083 <+19>: xchg %eax,%ebp
0xffffffff816cc084 <+20>: (bad)
0xffffffff816cc085 <+21>: push %rbp
Now op1->flags == KPROBE_FLAG_OPTIMATED;
2. Register the kprobe for <func+9>, assume that is kp2, corresponding optimized_kprobe is op2.
register_kprobe(kp2)
register_aggr_kprobe
alloc_aggr_kprobe
__prepare_optimized_kprobe
arch_prepare_optimized_kprobe
__recover_optprobed_insn // copy original bytes from kp1->optinsn.copied_insn,
// jump address = <func+14>
3. disable kp1:
disable_kprobe(kp1)
__disable_kprobe
...
if (p == orig_p || aggr_kprobe_disabled(orig_p)) {
ret = disarm_kprobe(orig_p, true) // add op1 in unoptimizing_list, not unoptimized
orig_p->flags |= KPROBE_FLAG_DISABLED; // op1->flags == KPROBE_FLAG_OPTIMATED | KPROBE_FLAG_DISABLED
...
4. unregister kp2
__unregister_kprobe_top
...
if (!kprobe_disabled(ap) && !kprobes_all_disarmed) {
optimize_kprobe(op)
...
if (arch_check_optimized_kprobe(op) < 0) // because op1 has KPROBE_FLAG_DISABLED, here not return
return;
p->kp.flags |= KPROBE_FLAG_OPTIMIZED; // now op2 has KPROBE_FLAG_OPTIMIZED
}
"func" code now is:
0xffffffff816cc079 <+9>: int3
0xffffffff816cc07a <+10>: push %rsp
0xffffffff816cc07b <+11>: jmp 0xffffffffa0210000
0xffffffff816cc080 <+16>: incl 0xf(%rcx)
0xffffffff816cc083 <+19>: xchg %eax,%ebp
0xffffffff816cc084 <+20>: (bad)
0xffffffff816cc085 <+21>: push %rbp
5. if call "func", int3 handler call setup_detour_execution:
if (p->flags & KPROBE_FLAG_OPTIMIZED) {
...
regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
...
}
The code for the destination address is
0xffffffffa021072c: push %r12
0xffffffffa021072e: xor %r12d,%r12d
0xffffffffa0210731: jmp 0xffffffff816cb5ee <func+14>
However, <func+14> is not a valid start instruction address. As a result, an error occurs.
Cc: [email protected]
Fixes: f66c0447cca1 ("kprobes: Set unoptimized flag after unoptimizing code")
Signed-off-by: Yang Jihong <[email protected]>
---
arch/x86/kernel/kprobes/opt.c | 2 +-
include/linux/kprobes.h | 1 +
kernel/kprobes.c | 2 +-
3 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index f406bfa9a8cd..57b0037d0a99 100644
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -353,7 +353,7 @@ int arch_check_optimized_kprobe(struct optimized_kprobe *op)
for (i = 1; i < op->optinsn.size; i++) {
p = get_kprobe(op->kp.addr + i);
- if (p && !kprobe_disabled(p))
+ if (p && !kprobe_disarmed(p))
return -EEXIST;
}
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index ab39285f71a6..85a64cb95d75 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -379,6 +379,7 @@ DEFINE_INSN_CACHE_OPS(optinsn);
extern void wait_for_kprobe_optimizer(void);
bool optprobe_queued_unopt(struct optimized_kprobe *op);
+bool kprobe_disarmed(struct kprobe *p);
#else /* !CONFIG_OPTPROBES */
static inline void wait_for_kprobe_optimizer(void) { }
#endif /* CONFIG_OPTPROBES */
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 90b0fac6efa0..99c3f4de3e5c 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -458,7 +458,7 @@ static inline int kprobe_optready(struct kprobe *p)
}
/* Return true if the kprobe is disarmed. Note: p must be on hash list */
-static inline bool kprobe_disarmed(struct kprobe *p)
+bool kprobe_disarmed(struct kprobe *p)
{
struct optimized_kprobe *op;
--
2.30.GIT
On Thu, 16 Feb 2023 11:42:45 +0800
Yang Jihong <[email protected]> wrote:
> Fixed optkprobe issues, mainly related to the x86 architecture.
>
> Yang Jihong (2):
> x86/kprobes: Fix __recover_optprobed_insn check optimizing logic
> x86/kprobes: Fix arch_check_optimized_kprobe check within
> optimized_kprobe range
>
> arch/x86/kernel/kprobes/opt.c | 6 +++---
> include/linux/kprobes.h | 2 ++
> kernel/kprobes.c | 4 ++--
> 3 files changed, 7 insertions(+), 5 deletions(-)
Thanks for updating! These look good to me!
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Thank you,
>
> --
>
> Changes since v1:
> - Remove patch1 since there is already a fix patch.
> - Add "cc stable" and modify comment for patch2.
> - Use "kprobe_disarmed" instead of "kprobe_disabled" for patch3.
> - Add fix commmit and "cc stable" for patch3.
>
> 2.30.GIT
>
--
Masami Hiramatsu (Google) <[email protected]>