Patch "kprobes/x86: Fix kernel panic when certain exception-handling addresses are probed" has been added to the 3.18-stable tree

This is a note to let you know that I've just added the patch titled

kprobes/x86: Fix kernel panic when certain exception-handling addresses are probed

to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kprobes-x86-fix-kernel-panic-when-certain-exception-handling-addresses-are-probed.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Masami Hiramatsu <[email protected]>
Date: Wed, 1 Mar 2017 01:23:24 +0900
Subject: kprobes/x86: Fix kernel panic when certain exception-handling addresses are probed

From: Masami Hiramatsu <[email protected]>

commit 75013fb16f8484898eaa8d0b08fed942d790f029 upstream.

Fix to the exception table entry check by using probed address instead of the address of copied instruction.

This bug may cause unexpected kernel panic if user probe an address where an exception can happen which should be fixup by __ex_table (e.g. copy_from_user.)

Unless user puts a kprobe on such address, this doesn't cause any problem.

This bug has been introduced years ago, by commit:

464846888d9a ("x86/kprobes: Fix a bug which can modify kernel code permanently").

---
 arch/x86/kernel/kprobes/common.h |    2 +-
 arch/x86/kernel/kprobes/core.c   |    6 +++---
 arch/x86/kernel/kprobes/opt.c    |    2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

@@ -67,7 +67,7 @@
 #endif
 
 /* Ensure if the instruction can be boostable */
-extern int can_boost(kprobe_opcode_t *instruction);
+extern int can_boost(kprobe_opcode_t *instruction, void *addr);
 /* Recover instruction if given address is probed */
 extern unsigned long recover_probed_instruction(kprobe_opcode_t *buf,
 					 unsigned long addr);

@@ -163,12 +163,12 @@ NOKPROBE_SYMBOL(skip_prefixes);
  * Returns non-zero if opcode is boostable.
  * RIP relative instructions are adjusted at copying time in 64 bits mode
  */
-int can_boost(kprobe_opcode_t *opcodes)
+int can_boost(kprobe_opcode_t *opcodes, void *addr)
 {
 	kprobe_opcode_t opcode;
 	kprobe_opcode_t *orig_opcodes = opcodes;
 
-	if (search_exception_tables((unsigned long)opcodes))
+	if (search_exception_tables((unsigned long)addr))
 		return 0;	/* Page fault may occur on this address. */
 
 retry:

@@ -385,7 +385,7 @@ static int arch_copy_kprobe(struct kprob
 	 * __copy_instruction can modify the displacement of the instruction,
 	 * but it doesn't affect boostable check.
 	 */
-	if (can_boost(p->ainsn.insn))
+	if (can_boost(p->ainsn.insn, p->addr))
 		p->ainsn.boostable = 0;
 	else
 		p->ainsn.boostable = -1;

@@ -177,7 +177,7 @@ static int copy_optimized_instructions(u
 
 	while (len < RELATIVEJUMP_SIZE) {
 		ret = __copy_instruction(dest + len, src + len);
-		if (!ret || !can_boost(dest + len))
+		if (!ret || !can_boost(dest + len, src + len))
 			return -EINVAL;
 		len += ret;
 	}

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/kprobes-x86-fix-kernel-panic-when-certain-exception-handling-addresses-are-probed.patch