tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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x86: Fix bit corruption at CPU resume time

In commit 78d77df71510 ("x86-64, init: Do not set NX bits on non-NX
capable hardware") we added the early_pmd_flags that gets the NX bit set
when a CPU supports NX. However, the new variable was marked __initdata,
because the main _use_ of this is in an __init routine.

However, the bit setting happens from secondary_startup_64(), which is
called not only at bootup, but on every secondary CPU start. Including
resuming from STR and at CPU hotplug time. So the value cannot be
__initdata.

Reported-bisected-and-tested-by: Michal Hocko <mhocko@suse.cz>
Cc: stable@vger.kernel.org # v3.9
Acked-by: Peter Anvin <hpa@linux.intel.com>
Cc: Fernando Luis Vázquez Cao <fernando@oss.ntt.co.jp>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Linus Torvalds 5e427ec2 2c2c0e52

+1 -1
+1 -1
arch/x86/kernel/head64.c
··· 34 34 extern pgd_t early_level4_pgt[PTRS_PER_PGD]; 35 35 extern pmd_t early_dynamic_pgts[EARLY_DYNAMIC_PAGE_TABLES][PTRS_PER_PMD]; 36 36 static unsigned int __initdata next_early_pgt = 2; 37 - pmdval_t __initdata early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX); 37 + pmdval_t early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX); 38 38 39 39 /* Wipe all early page tables except for the kernel symbol map */ 40 40 static void __init reset_early_page_tables(void)