Re: [syzbot] [syzbot] [hfs?] KASAN: slab-use-after-free Read in hfsplus_read_wrapper (2)

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Subject: [syzbot] [hfs?] KASAN: slab-use-after-free Read in hfsplus_read_wrapper (2)
Author: lizhi.xu@windriver.com

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git fe46a7dd189e

diff --git a/fs/hfsplus/wrapper.c b/fs/hfsplus/wrapper.c
index ce9346099c72..31ae9f95c3aa 100644
--- a/fs/hfsplus/wrapper.c
+++ b/fs/hfsplus/wrapper.c
@@ -179,16 +179,13 @@ int hfsplus_read_wrapper(struct super_block *sb)
 	sbi->s_vhdr_buf = kmalloc(hfsplus_min_io_size(sb), GFP_KERNEL);
 	if (!sbi->s_vhdr_buf)
 		goto out;
-	sbi->s_backup_vhdr_buf = kmalloc(hfsplus_min_io_size(sb), GFP_KERNEL);
-	if (!sbi->s_backup_vhdr_buf)
-		goto out_free_vhdr;
 
 reread:
 	error = hfsplus_submit_bio(sb, part_start + HFSPLUS_VOLHEAD_SECTOR,
 				   sbi->s_vhdr_buf, (void **)&sbi->s_vhdr,
 				   REQ_OP_READ);
 	if (error)
-		goto out_free_backup_vhdr;
+		goto out_free_vhdr;
 
 	error = -EINVAL;
 	switch (sbi->s_vhdr->signature) {
@@ -199,7 +196,7 @@ int hfsplus_read_wrapper(struct super_block *sb)
 		break;
 	case cpu_to_be16(HFSP_WRAP_MAGIC):
 		if (!hfsplus_read_mdb(sbi->s_vhdr, &wd))
-			goto out_free_backup_vhdr;
+			goto out_free_vhdr;
 		wd.ablk_size >>= HFSPLUS_SECTOR_SHIFT;
 		part_start += (sector_t)wd.ablk_start +
 			       (sector_t)wd.embed_start * wd.ablk_size;
@@ -212,10 +209,13 @@ int hfsplus_read_wrapper(struct super_block *sb)
 		 * (should do this only for cdrom/loop though)
 		 */
 		if (hfs_part_find(sb, &part_start, &part_size))
-			goto out_free_backup_vhdr;
+			goto out_free_vhdr;
 		goto reread;
 	}
 
+	sbi->s_backup_vhdr_buf = kmalloc(hfsplus_min_io_size(sb), GFP_KERNEL);
+	if (!sbi->s_backup_vhdr_buf)
+		goto out_free_backup_vhdr;
 	error = hfsplus_submit_bio(sb, part_start + part_size - 2,
 				   sbi->s_backup_vhdr_buf,
 				   (void **)&sbi->s_backup_vhdr, REQ_OP_READ);
-- 
2.43.0