[PATCH AUTOSEL 4.19 082/219] kprobes: Blacklist symbols in arch-defined prohibited area

Sasha Levin
2019-11-22T06:26:48Z

From: Masami Hiramatsu <mhiramat@kernel.org>

[ Upstream commit fb1a59fae8baa3f3c69b72a87ff94fc4fa5683ec ]

Blacklist symbols in arch-defined probe-prohibited areas.
With this change, user can see all symbols which are prohibited
to probe in debugfs.

All archtectures which have custom prohibit areas should define
its own arch_populate_kprobe_blacklist() function, but unless that,
all symbols marked __kprobes are blacklisted.

Reported-by: Andrea Righi <righi.andrea@gmail.com>
Tested-by: Andrea Righi <righi.andrea@gmail.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David S. Miller <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yonghong Song <yhs@fb.com>
Link: http://lkml.kernel.org/r/154503485491.26176.15823229545155174796.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/kprobes.h | 3 ++
kernel/kprobes.c | 67 ++++++++++++++++++++++++++++++++---------
2 files changed, 56 insertions(+), 14 deletions(-)

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 32cae0f35b9d4..9adb92ad24d3f 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -243,10 +243,13 @@ extern int arch_init_kprobes(void);
extern void show_registers(struct pt_regs *regs);
extern void kprobes_inc_nmissed_count(struct kprobe *p);
extern bool arch_within_kprobe_blacklist(unsigned long addr);
+extern int arch_populate_kprobe_blacklist(void);
extern bool arch_kprobe_on_func_entry(unsigned long offset);
extern bool kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym, unsigned long offset);

extern bool within_kprobe_blacklist(unsigned long addr);
+extern int kprobe_add_ksym_blacklist(unsigned long entry);
+extern int kprobe_add_area_blacklist(unsigned long start, unsigned long end);

struct kprobe_insn_cache {
struct mutex mutex;
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index b8efca9dc2cbb..c4f1acb2e7d20 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2090,6 +2090,47 @@ void dump_kprobe(struct kprobe *kp)
}
NOKPROBE_SYMBOL(dump_kprobe);

+int kprobe_add_ksym_blacklist(unsigned long entry)
+{
+ struct kprobe_blacklist_entry *ent;
+ unsigned long offset = 0, size = 0;
+
+ if (!kernel_text_address(entry) ||
+ !kallsyms_lookup_size_offset(entry, &size, &offset))
+ return -EINVAL;
+
+ ent = kmalloc(sizeof(*ent), GFP_KERNEL);
+ if (!ent)
+ return -ENOMEM;
+ ent->start_addr = entry;
+ ent->end_addr = entry + size;
+ INIT_LIST_HEAD(&ent->list);
+ list_add_tail(&ent->list, &kprobe_blacklist);
+
+ return (int)size;
+}
+
+/* Add all symbols in given area into kprobe blacklist */
+int kprobe_add_area_blacklist(unsigned long start, unsigned long end)
+{
+ unsigned long entry;
+ int ret = 0;
+
+ for (entry = start; entry < end; entry += ret) {
+ ret = kprobe_add_ksym_blacklist(entry);
+ if (ret < 0)
+ return ret;
+ if (ret == 0) /* In case of alias symbol */
+ ret = 1;
+ }
+ return 0;
+}
+
+int __init __weak arch_populate_kprobe_blacklist(void)
+{
+ return 0;
+}
+
/*
* Lookup and populate the kprobe_blacklist.
*
@@ -2101,26 +2142,24 @@ NOKPROBE_SYMBOL(dump_kprobe);
static int __init populate_kprobe_blacklist(unsigned long *start,
unsigned long *end)
{
+ unsigned long entry;
unsigned long *iter;
- struct kprobe_blacklist_entry *ent;
- unsigned long entry, offset = 0, size = 0;
+ int ret;

for (iter = start; iter < end; iter++) {
entry = arch_deref_entry_point((void *)*iter);
-
- if (!kernel_text_address(entry) ||
- !kallsyms_lookup_size_offset(entry, &size, &offset))
+ ret = kprobe_add_ksym_blacklist(entry);
+ if (ret == -EINVAL)
continue;
-
- ent = kmalloc(sizeof(*ent), GFP_KERNEL);
- if (!ent)
- return -ENOMEM;
- ent->start_addr = entry;
- ent->end_addr = entry + size;
- INIT_LIST_HEAD(&ent->list);
- list_add_tail(&ent->list, &kprobe_blacklist);
+ if (ret < 0)
+ return ret;
}
- return 0;
+
+ /* Symbols in __kprobes_text are blacklisted */
+ ret = kprobe_add_area_blacklist((unsigned long)__kprobes_text_start,
+ (unsigned long)__kprobes_text_end);
+
+ return ret ? : arch_populate_kprobe_blacklist();
}

/* Module notifier call back, checking kprobes on the module */
--
2.20.1