Using uninitialized_var() is dangerous as it papers over real bugs[1] (or can in the future), and suppresses unrelated compiler warnings (e.g. "unused variable"). If the compiler thinks it is uninitialized, either simply initialize the variable or make compiler changes. As a precursor to removing[2] this[3] macro[4], refactor code to avoid its need. The original reason for its use here was to work around the #ifdef being the only place the variable was used. This is better expressed using IS_ENABLED() and a new code block where the variable can be used unconditionally. [1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@xxxxxxxxxx/ [2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@xxxxxxxxxxxxxx/ [3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@xxxxxxxxxxxxxx/ [4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@xxxxxxxxxxxxxx/ Fixes: 1e01979c8f50 ("x86, numa: Implement pfn -> nid mapping granularity check") Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- arch/x86/mm/numa.c | 18 +++++++++--------- include/linux/page-flags-layout.h | 4 +++- 2 files changed, 12 insertions(+), 10 deletions(-) diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c index 8ee952038c80..b05f45e5e8e2 100644 --- a/arch/x86/mm/numa.c +++ b/arch/x86/mm/numa.c @@ -543,7 +543,6 @@ static void __init numa_clear_kernel_node_hotplug(void) static int __init numa_register_memblks(struct numa_meminfo *mi) { - unsigned long uninitialized_var(pfn_align); int i, nid; /* Account for nodes with cpus and no memory */ @@ -571,15 +570,16 @@ static int __init numa_register_memblks(struct numa_meminfo *mi) * If sections array is gonna be used for pfn -> nid mapping, check * whether its granularity is fine enough. */ -#ifdef NODE_NOT_IN_PAGE_FLAGS - pfn_align = node_map_pfn_alignment(); - if (pfn_align && pfn_align < PAGES_PER_SECTION) { - printk(KERN_WARNING "Node alignment %LuMB < min %LuMB, rejecting NUMA config\n", - PFN_PHYS(pfn_align) >> 20, - PFN_PHYS(PAGES_PER_SECTION) >> 20); - return -EINVAL; + if (IS_ENABLED(NODE_NOT_IN_PAGE_FLAGS)) { + unsigned long pfn_align = node_map_pfn_alignment(); + + if (pfn_align && pfn_align < PAGES_PER_SECTION) { + pr_warn("Node alignment %LuMB < min %LuMB, rejecting NUMA config\n", + PFN_PHYS(pfn_align) >> 20, + PFN_PHYS(PAGES_PER_SECTION) >> 20); + return -EINVAL; + } } -#endif if (!numa_meminfo_cover_memory(mi)) return -EINVAL; diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h index 71283739ffd2..e200eef6a7fd 100644 --- a/include/linux/page-flags-layout.h +++ b/include/linux/page-flags-layout.h @@ -98,9 +98,11 @@ /* * We are going to use the flags for the page to node mapping if its in * there. This includes the case where there is no node, so it is implicit. + * Note that this #define MUST have a value so that it can be tested with + * the IS_ENABLED() macro. */ #if !(NODES_WIDTH > 0 || NODES_SHIFT == 0) -#define NODE_NOT_IN_PAGE_FLAGS +#define NODE_NOT_IN_PAGE_FLAGS 1 #endif #if defined(CONFIG_NUMA_BALANCING) && LAST_CPUPID_WIDTH == 0 -- 2.25.1
