4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mahesh Salgaonkar <mahesh@xxxxxxxxxxxxxxxxxx> [ Upstream commit 74e96bf44f430cf7a01de19ba6cf49b361cdfd6e ] The global mce data buffer that used to copy rtas error log is of 2048 (RTAS_ERROR_LOG_MAX) bytes in size. Before the copy we read extended_log_length from rtas error log header, then use max of extended_log_length and RTAS_ERROR_LOG_MAX as a size of data to be copied. Ideally the platform (phyp) will never send extended error log with size > 2048. But if that happens, then we have a risk of buffer overrun and corruption. Fix this by using min_t instead. Fixes: d368514c3097 ("powerpc: Fix corruption when grabbing FWNMI data") Reported-by: Michal Suchanek <msuchanek@xxxxxxxx> Signed-off-by: Mahesh Salgaonkar <mahesh@xxxxxxxxxxxxxxxxxx> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/powerpc/platforms/pseries/ras.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/arch/powerpc/platforms/pseries/ras.c +++ b/arch/powerpc/platforms/pseries/ras.c @@ -357,7 +357,7 @@ static struct rtas_error_log *fwnmi_get_ int len, error_log_length; error_log_length = 8 + rtas_error_extended_log_length(h); - len = max_t(int, error_log_length, RTAS_ERROR_LOG_MAX); + len = min_t(int, error_log_length, RTAS_ERROR_LOG_MAX); memset(global_mce_data_buf, 0, RTAS_ERROR_LOG_MAX); memcpy(global_mce_data_buf, h, len); errhdr = (struct rtas_error_log *)global_mce_data_buf;