linux-kernel - [PATCH] x86/mm/mem_encrypt: fix a crash with kmemleak

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Message-Id: <20190409040502.55361-1-cai@lca.pw>
Date:   Tue,  9 Apr 2019 00:05:02 -0400
From:   Qian Cai <cai@....pw>
To:     dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org
Cc:     catalin.marinas@....com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, linux-kernel@...r.kernel.org,
        Qian Cai <cai@....pw>
Subject: [PATCH] x86/mm/mem_encrypt: fix a crash with kmemleak_scan

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@....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);
 }
 
-- 
2.17.2 (Apple Git-113)