uprobe: Do not emulate/sstep original instruction when ip is changed

If uprobe handler changes instruction pointer we still execute single
step) or emulate the original instruction and increment the (new) ip
with its length.

This makes the new instruction pointer bogus and application will
likely crash on illegal instruction execution.

If user decided to take execution elsewhere, it makes little sense
to execute the original instruction, so let's skip it.

Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20250916215301.664963-3-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 7ca1940607bd8340d2f4d1b74faccd40c1cfdc70..2b32c32bcb776fb4c7241f6fdde7b2d09898d232 100644 (file)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -2741,6 +2741,13 @@ static void handle_swbp(struct pt_regs *regs)
 
        handler_chain(uprobe, regs);
 
+       /*
+        * If user decided to take execution elsewhere, it makes little sense
+        * to execute the original instruction, so let's skip it.
+        */
+       if (instruction_pointer(regs) != bp_vaddr)
+               goto out;
+
        if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
                goto out;