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From 647a5c33e1c94054d7b63168cd6c12901591cb77 Mon Sep 17 00:00:00 2001
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From: Lianbo Jiang <lijiang@redhat.com>
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Date: Thu, 27 May 2021 18:02:11 +0800
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Subject: [PATCH] Fix for "kmem -s|-S" option on Linux 5.7 and later kernels
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Linux 5.7 and later kernels that contain kernel commit 1ad53d9fa3f6
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("slub: improve bit diffusion for freelist ptr obfuscation") changed
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the calculation formula in the freelist_ptr(), which added a swab()
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call to mix bits a little more. When kernel is configured with the
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"CONFIG_SLAB_FREELIST_HARDENED=y", without the patch, the "kmem -s|-S"
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options display wrong statistics and state whether slab objects are
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in use or free and can print the following errors:
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crash> kmem -s
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CACHE OBJSIZE ALLOCATED TOTAL SLABS SSIZE NAME
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87201e00 528 0 0 0 8k xfs_dqtrx
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87201f00 496 0 0 0 8k xfs_dquot
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kmem: xfs_buf: slab: 37202e6e900 invalid freepointer: b844bab900001d70
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kmem: xfs_buf: slab: 3720250fd80 invalid freepointer: b8603f9400001370
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...
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Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
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---
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memory.c | 9 +++++++--
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1 file changed, 7 insertions(+), 2 deletions(-)
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diff --git a/memory.c b/memory.c
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index 8c6bbe409922..a3cf8a86728d 100644
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--- a/memory.c
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+++ b/memory.c
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@@ -20,6 +20,7 @@
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#include <sys/mman.h>
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#include <ctype.h>
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#include <netinet/in.h>
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+#include <byteswap.h>
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struct meminfo { /* general purpose memory information structure */
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ulong cache; /* used by the various memory searching/dumping */
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@@ -19336,10 +19337,14 @@ count_free_objects(struct meminfo *si, ulong freelist)
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static ulong
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freelist_ptr(struct meminfo *si, ulong ptr, ulong ptr_addr)
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{
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- if (VALID_MEMBER(kmem_cache_random))
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+ if (VALID_MEMBER(kmem_cache_random)) {
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/* CONFIG_SLAB_FREELIST_HARDENED */
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+
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+ if (THIS_KERNEL_VERSION >= LINUX(5,7,0))
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+ ptr_addr = (sizeof(long) == 8) ? bswap_64(ptr_addr)
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+ : bswap_32(ptr_addr);
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return (ptr ^ si->random ^ ptr_addr);
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- else
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+ } else
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return ptr;
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}
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--
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2.30.2
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