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authorQian Cai <cai@lca.pw>2019-04-23 12:58:11 -0400
committerBorislav Petkov <bp@suse.de>2019-04-24 11:32:34 +0200
commit0d02113b31b2017dd349ec9df2314e798a90fa6e (patch)
tree46e965be16d06e42c150950286f05f3797c64ccb
parent36f0c423552dacaca152324b8e9bda42a6d88865 (diff)
download96b-common-0d02113b31b2017dd349ec9df2314e798a90fa6e.tar.gz
x86/mm: Fix a crash with kmemleak_scan()
The first kmemleak_scan() call after boot would trigger the crash below because this callpath: kernel_init free_initmem mem_encrypt_free_decrypted_mem free_init_pages unmaps memory inside the .bss when DEBUG_PAGEALLOC=y. kmemleak_init() will register the .data/.bss sections and then kmemleak_scan() will scan those addresses and dereference them looking for pointer references. If free_init_pages() frees and unmaps pages in those sections, kmemleak_scan() will crash if referencing one of those addresses: BUG: unable to handle kernel paging request at ffffffffbd402000 CPU: 12 PID: 325 Comm: kmemleak Not tainted 5.1.0-rc4+ #4 RIP: 0010:scan_block Call Trace: scan_gray_list kmemleak_scan kmemleak_scan_thread kthread ret_from_fork Since kmemleak_free_part() is tolerant to unknown objects (not tracked by kmemleak), it is fine to call it from free_init_pages() even if not all address ranges passed to this function are known to kmemleak. [ bp: Massage. ] Fixes: b3f0907c71e0 ("x86/mm: Add .bss..decrypted section to hold shared variables") Signed-off-by: Qian Cai <cai@lca.pw> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Brijesh Singh <brijesh.singh@amd.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190423165811.36699-1-cai@lca.pw
-rw-r--r--arch/x86/mm/init.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index f905a2371080..8dacdb96899e 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -5,6 +5,7 @@
#include <linux/memblock.h>
#include <linux/swapfile.h>
#include <linux/swapops.h>
+#include <linux/kmemleak.h>
#include <asm/set_memory.h>
#include <asm/e820/api.h>
@@ -766,6 +767,11 @@ void free_init_pages(const char *what, unsigned long begin, unsigned long end)
if (debug_pagealloc_enabled()) {
pr_info("debug: unmapping init [mem %#010lx-%#010lx]\n",
begin, end - 1);
+ /*
+ * Inform kmemleak about the hole in the memory since the
+ * corresponding pages will be unmapped.
+ */
+ kmemleak_free_part((void *)begin, end - begin);
set_memory_np(begin, (end - begin) >> PAGE_SHIFT);
} else {
/*