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x86/mm/numa: Remove uninitialized_var() usage

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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@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Fixes: 1e01979c8f ("x86, numa: Implement pfn -> nid mapping granularity check")
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2020-06-03 13:28:45 -07:00
parent 4b19bec97c
commit aecfd220b2
2 changed files with 12 additions and 10 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

18
arch/x86/mm/numa.c
View file

@ -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;

4
include/linux/page-flags-layout.h
View file

@ -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