From: Qian Cai cai@lca.pw
[ Upstream commit 0d02113b31b2017dd349ec9df2314e798a90fa6e ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/mm/init.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index d883869437b5..fb5f29c60019 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -6,6 +6,7 @@ #include <linux/bootmem.h> /* for max_low_pfn */ #include <linux/swapfile.h> #include <linux/swapops.h> +#include <linux/kmemleak.h>
#include <asm/set_memory.h> #include <asm/e820/api.h> @@ -767,6 +768,11 @@ void free_init_pages(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 { /*