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

[ Upstream commit 4363264111e1297fa37aa39b0598faa19298ecca ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 6285674412f2571692c59dcff1eea426bd00d2c8..2b809bc849dd633b83c8e63a3d41743d0e6e18d2 100644 (file)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -2248,6 +2248,13 @@ 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;