[PATCH v6 3/6] mce: fix set_mce_nospec to always unmap the whole page
From: Jane Chu
Date: Sat Mar 19 2022 - 02:30:10 EST
Mark poisoned page as not present, and to reverse the 'np' effect,
restate the _PAGE_PRESENT bit. Please refer to discussions here for
reason behind the decision.
https://lore.kernel.org/all/CAPcyv4hrXPb1tASBZUg-GgdVs0OOFKXMXLiHmktg_kFi7YBMyQ@xxxxxxxxxxxxxx/
Now since poisoned page is marked as not-present, in order to
avoid writing to a 'np' page and trigger kernel Oops, also fix
pmem_do_write().
Fixes: 284ce4011ba6 ("x86/memory_failure: Introduce {set, clear}_mce_nospec()")
Signed-off-by: Jane Chu <jane.chu@xxxxxxxxxx>
---
arch/x86/kernel/cpu/mce/core.c | 6 +++---
arch/x86/mm/pat/set_memory.c | 21 +++++++++------------
drivers/nvdimm/pmem.c | 31 +++++++------------------------
include/linux/set_memory.h | 4 ++--
4 files changed, 21 insertions(+), 41 deletions(-)
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 5818b837fd4d..8d12739f283d 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -613,7 +613,7 @@ static int uc_decode_notifier(struct notifier_block *nb, unsigned long val,
pfn = mce->addr >> PAGE_SHIFT;
if (!memory_failure(pfn, 0)) {
- set_mce_nospec(pfn, whole_page(mce));
+ set_mce_nospec(pfn);
mce->kflags |= MCE_HANDLED_UC;
}
@@ -1297,7 +1297,7 @@ static void kill_me_maybe(struct callback_head *cb)
ret = memory_failure(p->mce_addr >> PAGE_SHIFT, flags);
if (!ret) {
- set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page);
+ set_mce_nospec(p->mce_addr >> PAGE_SHIFT);
sync_core();
return;
}
@@ -1321,7 +1321,7 @@ static void kill_me_never(struct callback_head *cb)
p->mce_count = 0;
pr_err("Kernel accessed poison in user space at %llx\n", p->mce_addr);
if (!memory_failure(p->mce_addr >> PAGE_SHIFT, 0))
- set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page);
+ set_mce_nospec(p->mce_addr >> PAGE_SHIFT);
}
static void queue_task_work(struct mce *m, char *msg, void (*func)(struct callback_head *))
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 9abc6077d768..747614c3dd83 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1925,14 +1925,14 @@ int set_memory_wb(unsigned long addr, int numpages)
}
EXPORT_SYMBOL(set_memory_wb);
+static int _set_memory_present(unsigned long addr, int numpages)
+{
+ return change_page_attr_set(&addr, numpages, __pgprot(_PAGE_PRESENT), 0);
+}
+
#ifdef CONFIG_X86_64
-/*
- * Prevent speculative access to the page by either unmapping
- * it (if we do not require access to any part of the page) or
- * marking it uncacheable (if we want to try to retrieve data
- * from non-poisoned lines in the page).
- */
-int set_mce_nospec(unsigned long pfn, bool unmap)
+/* Prevent speculative access to a page by marking it not-present */
+int set_mce_nospec(unsigned long pfn)
{
unsigned long decoy_addr;
int rc;
@@ -1954,10 +1954,7 @@ int set_mce_nospec(unsigned long pfn, bool unmap)
*/
decoy_addr = (pfn << PAGE_SHIFT) + (PAGE_OFFSET ^ BIT(63));
- if (unmap)
- rc = set_memory_np(decoy_addr, 1);
- else
- rc = set_memory_uc(decoy_addr, 1);
+ rc = set_memory_np(decoy_addr, 1);
if (rc)
pr_warn("Could not invalidate pfn=0x%lx from 1:1 map\n", pfn);
return rc;
@@ -1967,7 +1964,7 @@ EXPORT_SYMBOL(set_mce_nospec);
/* Restore full speculative operation to the pfn. */
int clear_mce_nospec(unsigned long pfn)
{
- return set_memory_wb((unsigned long) pfn_to_kaddr(pfn), 1);
+ return _set_memory_present((unsigned long) pfn_to_kaddr(pfn), 1);
}
EXPORT_SYMBOL(clear_mce_nospec);
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 58d95242a836..30c71a68175b 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -158,36 +158,19 @@ static blk_status_t pmem_do_write(struct pmem_device *pmem,
struct page *page, unsigned int page_off,
sector_t sector, unsigned int len)
{
- blk_status_t rc = BLK_STS_OK;
- bool bad_pmem = false;
phys_addr_t pmem_off = sector * 512 + pmem->data_offset;
void *pmem_addr = pmem->virt_addr + pmem_off;
- if (unlikely(is_bad_pmem(&pmem->bb, sector, len)))
- bad_pmem = true;
+ if (unlikely(is_bad_pmem(&pmem->bb, sector, len))) {
+ blk_status_t rc = pmem_clear_poison(pmem, pmem_off, len);
- /*
- * Note that we write the data both before and after
- * clearing poison. The write before clear poison
- * handles situations where the latest written data is
- * preserved and the clear poison operation simply marks
- * the address range as valid without changing the data.
- * In this case application software can assume that an
- * interrupted write will either return the new good
- * data or an error.
- *
- * However, if pmem_clear_poison() leaves the data in an
- * indeterminate state we need to perform the write
- * after clear poison.
- */
+ if (rc != BLK_STS_OK)
+ pr_warn_ratelimited("%s: failed to clear poison\n", __func__);
+ return rc;
+ }
flush_dcache_page(page);
write_pmem(pmem_addr, page, page_off, len);
- if (unlikely(bad_pmem)) {
- rc = pmem_clear_poison(pmem, pmem_off, len);
- write_pmem(pmem_addr, page, page_off, len);
- }
-
- return rc;
+ return BLK_STS_OK;
}
static void pmem_submit_bio(struct bio *bio)
diff --git a/include/linux/set_memory.h b/include/linux/set_memory.h
index d6263d7afb55..cde2d8687a7b 100644
--- a/include/linux/set_memory.h
+++ b/include/linux/set_memory.h
@@ -43,10 +43,10 @@ static inline bool can_set_direct_map(void)
#endif /* CONFIG_ARCH_HAS_SET_DIRECT_MAP */
#ifdef CONFIG_X86_64
-int set_mce_nospec(unsigned long pfn, bool unmap);
+int set_mce_nospec(unsigned long pfn);
int clear_mce_nospec(unsigned long pfn);
#else
-static inline int set_mce_nospec(unsigned long pfn, bool unmap)
+static inline int set_mce_nospec(unsigned long pfn)
{
return 0;
}
--
2.18.4