FAILED: patch "[PATCH] x86/mm: Prevent kernel Oops in PTDUMP code with HIGHPTE=y" failed to apply to 4.16-stable tree

PATCH [email protected] 1 participant 1 message Apr 24, 2018

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2018-04-24 10:05 UTC #0 lore raw

The patch below does not apply to the 4.16-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

Quoted 1 line

From d6ef1f194b7569af8b8397876dc9ab07649d63cb Mon Sep 17 00:00:00 2001

From: Joerg Roedel <[email protected]>
Date: Tue, 17 Apr 2018 15:27:16 +0200
Subject: [PATCH] x86/mm: Prevent kernel Oops in PTDUMP code with HIGHPTE=y

The walk_pte_level() function just uses __va to get the virtual address of the PTE page, but that breaks when the PTE page is not in the direct mapping with HIGHPTE=y.

The result is an unhandled kernel paging request at some random address when accessing the current_kernel or current_user file.

Use the correct API to access PTE pages.

Fixes fe770bf0310d ('x86: clean up the page table dumper and add 32-bit support')

Signed-off-by Joerg Roedel <[email protected]>

Signed-off-by Thomas Gleixner <[email protected]>

Cc [email protected]

Link https://lkml.kernel.org/r/[email protected] open here

arch/x86/mm/dump_pagetables.c +6 -5

index 62a7e9f65dec..cc7ff5957194 100644
@@ -18,6 +18,7 @@
 #include <linux/init.h>
 #include <linux/sched.h>
 #include <linux/seq_file.h>
+#include <linux/highmem.h>
 
 #include <asm/pgtable.h>

@@ -334,16 +335,16 @@ static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
 			   pgprotval_t eff_in, unsigned long P)
 {
 	int i;
-	pte_t *start;
+	pte_t *pte;
 	pgprotval_t prot, eff;
 
-	start = (pte_t *)pmd_page_vaddr(addr);
 	for (i = 0; i < PTRS_PER_PTE; i++) {
-		prot = pte_flags(*start);
-		eff = effective_prot(eff_in, prot);
 		st->current_address = normalize_addr(P + i * PTE_LEVEL_MULT);
+		pte = pte_offset_map(&addr, st->current_address);
+		prot = pte_flags(*pte);
+		eff = effective_prot(eff_in, prot);
 		note_page(m, st, __pgprot(prot), eff, 5);
-		start++;
+		pte_unmap(pte);
 	}
 }
 #ifdef CONFIG_KASAN