| From 0d02113b31b2017dd349ec9df2314e798a90fa6e Mon Sep 17 00:00:00 2001 |
| From: Qian Cai <cai@lca.pw> |
| Date: Tue, 23 Apr 2019 12:58:11 -0400 |
| Subject: x86/mm: Fix a crash with kmemleak_scan() |
| |
| From: Qian Cai <cai@lca.pw> |
| |
| commit 0d02113b31b2017dd349ec9df2314e798a90fa6e upstream. |
| |
| 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/x86/mm/init.c | 6 ++++++ |
| 1 file changed, 6 insertions(+) |
| |
| --- 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, u |
| 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 { |
| /* |
