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: b3f0907c71 ("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
0d02113b31