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Message-ID: <20230413131223.4135168-2-glider@google.com>
Date: Thu, 13 Apr 2023 15:12:21 +0200
From: Alexander Potapenko <glider@...gle.com>
To: glider@...gle.com
Cc: urezki@...il.com, hch@...radead.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, akpm@...ux-foundation.org, elver@...gle.com,
dvyukov@...gle.com, kasan-dev@...glegroups.com,
Dipanjan Das <mail.dipanjan.das@...il.com>
Subject: [PATCH v2 2/4] mm: kmsan: handle alloc failures in kmsan_ioremap_page_range()
Similarly to kmsan_vmap_pages_range_noflush(),
kmsan_ioremap_page_range() must also properly handle allocation/mapping
failures. In the case of such, it must clean up the already created
metadata mappings and return an error code, so that the error can be
propagated to ioremap_page_range(). Without doing so, KMSAN may silently
fail to bring the metadata for the page range into a consistent state,
which will result in user-visible crashes when trying to access them.
Reported-by: Dipanjan Das <mail.dipanjan.das@...il.com>
Link: https://lore.kernel.org/linux-mm/CANX2M5ZRrRA64k0hOif02TjmY9kbbO2aCBPyq79es34RXZ=cAw@mail.gmail.com/
Fixes: b073d7f8aee4 ("mm: kmsan: maintain KMSAN metadata for page operations")
Signed-off-by: Alexander Potapenko <glider@...gle.com>
---
v2:
-- updated patch description as requested by Andrew Morton
-- check the return value of __vmap_pages_range_noflush(), as suggested by Dipanjan Das
-- return 0 from the inline version of kmsan_ioremap_page_range()
(spotted by kernel test robot <lkp@...el.com>)
---
include/linux/kmsan.h | 19 ++++++++-------
mm/kmsan/hooks.c | 55 ++++++++++++++++++++++++++++++++++++-------
mm/vmalloc.c | 4 ++--
3 files changed, 59 insertions(+), 19 deletions(-)
diff --git a/include/linux/kmsan.h b/include/linux/kmsan.h
index c7ff3aefc5a13..30b17647ce3c7 100644
--- a/include/linux/kmsan.h
+++ b/include/linux/kmsan.h
@@ -160,11 +160,12 @@ void kmsan_vunmap_range_noflush(unsigned long start, unsigned long end);
* @page_shift: page_shift argument passed to vmap_range_noflush().
*
* KMSAN creates new metadata pages for the physical pages mapped into the
- * virtual memory.
+ * virtual memory. Returns 0 on success, callers must check for non-zero return
+ * value.
*/
-void kmsan_ioremap_page_range(unsigned long addr, unsigned long end,
- phys_addr_t phys_addr, pgprot_t prot,
- unsigned int page_shift);
+int kmsan_ioremap_page_range(unsigned long addr, unsigned long end,
+ phys_addr_t phys_addr, pgprot_t prot,
+ unsigned int page_shift);
/**
* kmsan_iounmap_page_range() - Notify KMSAN about a iounmap_page_range() call.
@@ -296,12 +297,12 @@ static inline void kmsan_vunmap_range_noflush(unsigned long start,
{
}
-static inline void kmsan_ioremap_page_range(unsigned long start,
- unsigned long end,
- phys_addr_t phys_addr,
- pgprot_t prot,
- unsigned int page_shift)
+static inline int kmsan_ioremap_page_range(unsigned long start,
+ unsigned long end,
+ phys_addr_t phys_addr, pgprot_t prot,
+ unsigned int page_shift)
{
+ return 0;
}
static inline void kmsan_iounmap_page_range(unsigned long start,
diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c
index 3807502766a3e..ec0da72e65aa0 100644
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -148,35 +148,74 @@ void kmsan_vunmap_range_noflush(unsigned long start, unsigned long end)
* into the virtual memory. If those physical pages already had shadow/origin,
* those are ignored.
*/
-void kmsan_ioremap_page_range(unsigned long start, unsigned long end,
- phys_addr_t phys_addr, pgprot_t prot,
- unsigned int page_shift)
+int kmsan_ioremap_page_range(unsigned long start, unsigned long end,
+ phys_addr_t phys_addr, pgprot_t prot,
+ unsigned int page_shift)
{
gfp_t gfp_mask = GFP_KERNEL | __GFP_ZERO;
struct page *shadow, *origin;
unsigned long off = 0;
- int nr;
+ int nr, err = 0, clean = 0, mapped;
if (!kmsan_enabled || kmsan_in_runtime())
- return;
+ return 0;
nr = (end - start) / PAGE_SIZE;
kmsan_enter_runtime();
- for (int i = 0; i < nr; i++, off += PAGE_SIZE) {
+ for (int i = 0; i < nr; i++, off += PAGE_SIZE, clean = i) {
shadow = alloc_pages(gfp_mask, 1);
origin = alloc_pages(gfp_mask, 1);
- __vmap_pages_range_noflush(
+ if (!shadow || !origin) {
+ err = -ENOMEM;
+ goto ret;
+ }
+ mapped = __vmap_pages_range_noflush(
vmalloc_shadow(start + off),
vmalloc_shadow(start + off + PAGE_SIZE), prot, &shadow,
PAGE_SHIFT);
- __vmap_pages_range_noflush(
+ if (mapped) {
+ err = mapped;
+ goto ret;
+ }
+ shadow = NULL;
+ mapped = __vmap_pages_range_noflush(
vmalloc_origin(start + off),
vmalloc_origin(start + off + PAGE_SIZE), prot, &origin,
PAGE_SHIFT);
+ if (mapped) {
+ __vunmap_range_noflush(
+ vmalloc_shadow(start + off),
+ vmalloc_shadow(start + off + PAGE_SIZE));
+ err = mapped;
+ goto ret;
+ }
+ origin = NULL;
+ }
+ /* Page mapping loop finished normally, nothing to clean up. */
+ clean = 0;
+
+ret:
+ if (clean > 0) {
+ /*
+ * Something went wrong. Clean up shadow/origin pages allocated
+ * on the last loop iteration, then delete mappings created
+ * during the previous iterations.
+ */
+ if (shadow)
+ __free_pages(shadow, 1);
+ if (origin)
+ __free_pages(origin, 1);
+ __vunmap_range_noflush(
+ vmalloc_shadow(start),
+ vmalloc_shadow(start + clean * PAGE_SIZE));
+ __vunmap_range_noflush(
+ vmalloc_origin(start),
+ vmalloc_origin(start + clean * PAGE_SIZE));
}
flush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));
flush_cache_vmap(vmalloc_origin(start), vmalloc_origin(end));
kmsan_leave_runtime();
+ return err;
}
void kmsan_iounmap_page_range(unsigned long start, unsigned long end)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 1355d95cce1ca..31ff782d368b0 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -313,8 +313,8 @@ int ioremap_page_range(unsigned long addr, unsigned long end,
ioremap_max_page_shift);
flush_cache_vmap(addr, end);
if (!err)
- kmsan_ioremap_page_range(addr, end, phys_addr, prot,
- ioremap_max_page_shift);
+ err = kmsan_ioremap_page_range(addr, end, phys_addr, prot,
+ ioremap_max_page_shift);
return err;
}
--
2.40.0.577.gac1e443424-goog
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