Messages in this thread | | | Date | Tue, 16 Apr 2019 19:11:04 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86/mm/mem_encrypt: fix a crash with kmemleak_scan |
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+ Brijesh.
On Tue, Apr 09, 2019 at 12:05:02AM -0400, Qian Cai wrote: > The first kmemleak_scan() after boot would trigger a crash below because > > kernel_init > free_initmem > mem_encrypt_free_decrypted_mem > free_init_pages > > unmapped some memory inside the .bss. > > 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+0x58/0x160 > Call Trace: > scan_gray_list+0x1d9/0x280 > kmemleak_scan+0x485/0xad0 > kmemleak_scan_thread+0x9f/0xc4 > kthread+0x1d2/0x1f0 > ret_from_fork+0x35/0x40 > > Signed-off-by: Qian Cai <cai@lca.pw> > --- > arch/x86/mm/mem_encrypt.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c > index 385afa2b9e17..614ab156024f 100644 > --- a/arch/x86/mm/mem_encrypt.c > +++ b/arch/x86/mm/mem_encrypt.c > @@ -18,6 +18,7 @@ > #include <linux/dma-direct.h> > #include <linux/swiotlb.h> > #include <linux/mem_encrypt.h> > +#include <linux/kmemleak.h> > > #include <asm/tlbflush.h> > #include <asm/fixmap.h> > @@ -369,6 +370,11 @@ void __init mem_encrypt_free_decrypted_mem(void) > } > } > > + /* > + * Inform kmemleak about the hole in the .bss section since the > + * corresponding pages will be unmapped with DEBUG_PAGEALLOC=y. > + */ > + kmemleak_free_part((void *)vaddr, vaddr_end - vaddr); > free_init_pages("unused decrypted", vaddr, vaddr_end);
I don't understand what the logic here is: we have a couple of other free_init_pages() calls but they don't have kmemleak_free_part() in front.
Now, if kmemleak needs to be told that memory is getting freed, why isn't kmemleak_free_part() called in free_init_pages() ?
This needs more explanation.
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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