Re: [syzbot] Re: KMSAN: uninit-value in __crc32c_le_base

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Subject: Re: KMSAN: uninit-value in __crc32c_le_base
Author: dmantipov@yandex.ru

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git cfaaa7d010d1fc58f9717fcc8591201e741d2d49

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index b11bfe68dd65..e0b515aa1c63 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -18,6 +18,9 @@
 #include <linux/crc32c.h>
 #include <linux/sched/mm.h>
 #include <linux/unaligned.h>
+#ifdef CONFIG_KMSAN
+#include <linux/kmsan-checks.h>
+#endif
 #include <crypto/hash.h>
 #include "ctree.h"
 #include "disk-io.h"
@@ -93,6 +96,10 @@ static void csum_tree_block(struct extent_buffer *buf, u8 *result)
 		num_pages = num_extent_pages(buf);
 	}
 
+#ifdef CONFIG_KMSAN
+	kmsan_unpoison_memory(kaddr + BTRFS_CSUM_SIZE,
+			      first_page_part - BTRFS_CSUM_SIZE);
+#endif
 	crypto_shash_update(shash, kaddr + BTRFS_CSUM_SIZE,
 			    first_page_part - BTRFS_CSUM_SIZE);
 
@@ -104,6 +111,9 @@ static void csum_tree_block(struct extent_buffer *buf, u8 *result)
 	 */
 	for (i = 1; i < num_pages && INLINE_EXTENT_BUFFER_PAGES > 1; i++) {
 		kaddr = folio_address(buf->folios[i]);
+#ifdef CONFIG_KMSAN
+		kmsan_unpoison_memory(kaddr, PAGE_SIZE);
+#endif
 		crypto_shash_update(shash, kaddr, PAGE_SIZE);
 	}
 	memset(result, 0, BTRFS_CSUM_SIZE);