kgdb: Prevent infinite recursive entries to the debugger

[ Upstream commit 3ca676e4ca60d1834bb77535dafe24169cadacef ]

If we detect that we recursively entered the debugger we should hack
our I/O ops to NULL so that the panic() in the next line won't
actually cause another recursion into the debugger.  The first line of
kgdb_panic() will check this and return.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20200507130644.v4.6.I89de39f68736c9de610e6f241e68d8dbc44bc266@changeid
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 950dc667c82343a699db08bd629176334cf5527c..d47c7d6656cd3beaf77202b470ef32708498f8f5 100644 (file)
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -532,6 +532,7 @@ static int kgdb_reenter_check(struct kgdb_state *ks)
 
        if (exception_level > 1) {
                dump_stack();
+               kgdb_io_module_registered = false;
                panic("Recursive entry to debugger");
        }