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authorPavel Tatashin <pasha.tatashin@oracle.com>2017-08-18 15:16:05 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-08-18 15:32:01 -0700
commit3010f876500f9ba921afaeccec30c45ca6584dc8 (patch)
tree61f656b6b3f56459f27cb11944102bf3dfcc162b
parent768dc4e48420955518974d8486c1b00ec05e7274 (diff)
downloadlinux-stericsson-3010f876500f9ba921afaeccec30c45ca6584dc8.tar.gz
mm: discard memblock data later
There is existing use after free bug when deferred struct pages are enabled: The memblock_add() allocates memory for the memory array if more than 128 entries are needed. See comment in e820__memblock_setup(): * The bootstrap memblock region count maximum is 128 entries * (INIT_MEMBLOCK_REGIONS), but EFI might pass us more E820 entries * than that - so allow memblock resizing. This memblock memory is freed here: free_low_memory_core_early() We access the freed memblock.memory later in boot when deferred pages are initialized in this path: deferred_init_memmap() for_each_mem_pfn_range() __next_mem_pfn_range() type = &memblock.memory; One possible explanation for why this use-after-free hasn't been hit before is that the limit of INIT_MEMBLOCK_REGIONS has never been exceeded at least on systems where deferred struct pages were enabled. Tested by reducing INIT_MEMBLOCK_REGIONS down to 4 from the current 128, and verifying in qemu that this code is getting excuted and that the freed pages are sane. Link: http://lkml.kernel.org/r/1502485554-318703-2-git-send-email-pasha.tatashin@oracle.com Fixes: 7e18adb4f80b ("mm: meminit: initialise remaining struct pages in parallel with kswapd") Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com> Reviewed-by: Steven Sistare <steven.sistare@oracle.com> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com> Reviewed-by: Bob Picco <bob.picco@oracle.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/memblock.h6
-rw-r--r--mm/memblock.c38
-rw-r--r--mm/nobootmem.c16
-rw-r--r--mm/page_alloc.c4
4 files changed, 25 insertions, 39 deletions
diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 77d427974f57..bae11c7e7bf3 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -61,6 +61,7 @@ extern int memblock_debug;
#ifdef CONFIG_ARCH_DISCARD_MEMBLOCK
#define __init_memblock __meminit
#define __initdata_memblock __meminitdata
+void memblock_discard(void);
#else
#define __init_memblock
#define __initdata_memblock
@@ -74,8 +75,6 @@ phys_addr_t memblock_find_in_range_node(phys_addr_t size, phys_addr_t align,
int nid, ulong flags);
phys_addr_t memblock_find_in_range(phys_addr_t start, phys_addr_t end,
phys_addr_t size, phys_addr_t align);
-phys_addr_t get_allocated_memblock_reserved_regions_info(phys_addr_t *addr);
-phys_addr_t get_allocated_memblock_memory_regions_info(phys_addr_t *addr);
void memblock_allow_resize(void);
int memblock_add_node(phys_addr_t base, phys_addr_t size, int nid);
int memblock_add(phys_addr_t base, phys_addr_t size);
@@ -110,6 +109,9 @@ void __next_mem_range_rev(u64 *idx, int nid, ulong flags,
void __next_reserved_mem_region(u64 *idx, phys_addr_t *out_start,
phys_addr_t *out_end);
+void __memblock_free_early(phys_addr_t base, phys_addr_t size);
+void __memblock_free_late(phys_addr_t base, phys_addr_t size);
+
/**
* for_each_mem_range - iterate through memblock areas from type_a and not
* included in type_b. Or just type_a if type_b is NULL.
diff --git a/mm/memblock.c b/mm/memblock.c
index 2cb25fe4452c..bf14aea6ab70 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -285,31 +285,27 @@ static void __init_memblock memblock_remove_region(struct memblock_type *type, u
}
#ifdef CONFIG_ARCH_DISCARD_MEMBLOCK
-
-phys_addr_t __init_memblock get_allocated_memblock_reserved_regions_info(
- phys_addr_t *addr)
-{
- if (memblock.reserved.regions == memblock_reserved_init_regions)
- return 0;
-
- *addr = __pa(memblock.reserved.regions);
-
- return PAGE_ALIGN(sizeof(struct memblock_region) *
- memblock.reserved.max);
-}
-
-phys_addr_t __init_memblock get_allocated_memblock_memory_regions_info(
- phys_addr_t *addr)
+/**
+ * Discard memory and reserved arrays if they were allocated
+ */
+void __init memblock_discard(void)
{
- if (memblock.memory.regions == memblock_memory_init_regions)
- return 0;
+ phys_addr_t addr, size;
- *addr = __pa(memblock.memory.regions);
+ if (memblock.reserved.regions != memblock_reserved_init_regions) {
+ addr = __pa(memblock.reserved.regions);
+ size = PAGE_ALIGN(sizeof(struct memblock_region) *
+ memblock.reserved.max);
+ __memblock_free_late(addr, size);
+ }
- return PAGE_ALIGN(sizeof(struct memblock_region) *
- memblock.memory.max);
+ if (memblock.memory.regions == memblock_memory_init_regions) {
+ addr = __pa(memblock.memory.regions);
+ size = PAGE_ALIGN(sizeof(struct memblock_region) *
+ memblock.memory.max);
+ __memblock_free_late(addr, size);
+ }
}
-
#endif
/**
diff --git a/mm/nobootmem.c b/mm/nobootmem.c
index 36454d0f96ee..3637809a18d0 100644
--- a/mm/nobootmem.c
+++ b/mm/nobootmem.c
@@ -146,22 +146,6 @@ static unsigned long __init free_low_memory_core_early(void)
NULL)
count += __free_memory_core(start, end);
-#ifdef CONFIG_ARCH_DISCARD_MEMBLOCK
- {
- phys_addr_t size;
-
- /* Free memblock.reserved array if it was allocated */
- size = get_allocated_memblock_reserved_regions_info(&start);
- if (size)
- count += __free_memory_core(start, start + size);
-
- /* Free memblock.memory array if it was allocated */
- size = get_allocated_memblock_memory_regions_info(&start);
- if (size)
- count += __free_memory_core(start, start + size);
- }
-#endif
-
return count;
}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6d00f746c2fd..1bad301820c7 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1584,6 +1584,10 @@ void __init page_alloc_init_late(void)
/* Reinit limits that are based on free pages after the kernel is up */
files_maxfiles_init();
#endif
+#ifdef CONFIG_ARCH_DISCARD_MEMBLOCK
+ /* Discard memblock private memory */
+ memblock_discard();
+#endif
for_each_populated_zone(zone)
set_zone_contiguous(zone);