[PATCH] s390/kprobes: Prevent kprobes on instructions with exception table entry

[Heiko Carstens]

The mvcos exception handler ex_handler_ua_mvcos() decodes the faulting
instruction, assuming it is an mvcos instruction. In case the instruction
is kprobed the decoded instruction is a breakpoint instruction instead,
which leads to incorrect instruction decoding and potential register
corruption.

Fix this by simply preventing to set a kprobe on such instructions,
similar like arm64 is doing it.

Fixes: c488f5187a24 ("s390/uaccess: Shorten raw_copy_from_user() / raw_copy_to_user() inline assemblies")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
---
 arch/s390/kernel/kprobes.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
index c450120b4474..e806b124e4ba 100644
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c
@@ -85,6 +85,9 @@ static bool can_probe(unsigned long paddr)
 	if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
 		return false;
 
+	if (s390_search_extables(paddr))
+		return false;
+
 	/* Decode instructions */
 	addr = paddr - offset;
 	while (addr < paddr) {
-- 
2.53.0