On 9/18/2018 3:03 AM, Matthias Kaehlcke wrote:
sysrq_handle_crash() dereferences a NULL pointer on purpose to force an exception, the local variable 'killer' is assigned to NULL and dereferenced later. Clang detects the NULL pointer dereference at compile time and emits a BRK instruction (on arm64) instead of the expected NULL pointer exception. Change 'killer' to a global variable (and rename it to 'sysrq_killer' to avoid possible clashes) to prevent Clang from detecting the condition. By default global variables are initialized with zero/NULL in C, therefore an explicit initialization is not needed.Reported-by: Sai Prakash Ranjan <saiprakash.ran...@codeaurora.org> Suggested-by: Evan Green <evgr...@chromium.org> Signed-off-by: Matthias Kaehlcke <m...@chromium.org> --- drivers/tty/sysrq.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index 06ed20dd01ba..49fa8e758690 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -132,10 +132,10 @@ static struct sysrq_key_op sysrq_unraw_op = { #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL) #endif /* CONFIG_VT */+char *sysrq_killer;+ static void sysrq_handle_crash(int key) { - char *killer = NULL; - /* we need to release the RCU read lock here, * otherwise we get an annoying * 'BUG: sleeping function called from invalid context' @@ -144,7 +144,7 @@ static void sysrq_handle_crash(int key) rcu_read_unlock(); panic_on_oops = 1; /* force panic */ wmb(); - *killer = 1; + *sysrq_killer = 1; } static struct sysrq_key_op sysrq_crash_op = { .handler = sysrq_handle_crash,
Tested-by: Sai Prakash Ranjan <saiprakash.ran...@codeaurora.org> -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
