From 0d02113b31b2017dd349ec9df2314e798a90fa6e Mon Sep 17 00:00:00 2001 From: Qian Cai Date: Tue, 23 Apr 2019 12:58:11 -0400 Subject: 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 Signed-off-by: Borislav Petkov Reviewed-by: Catalin Marinas Cc: Andy Lutomirski Cc: Brijesh Singh Cc: Dave Hansen Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: x86-ml Link: https://lkml.kernel.org/r/20190423165811.36699-1-cai@lca.pw --- 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 f905a2371080..8dacdb96899e 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -5,6 +5,7 @@ #include #include #include +#include #include #include @@ -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 { /* -- cgit v1.2.3-70-g09d2