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Subject: [PATCH] hfsplus: add debug printk to show partial reads in hfs_brec_read
Author: kartikey406@gmail.com


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

Debug patch to demonstrate how hfs_brec_read() can read less data than
requested when filesystem is corrupted, leaving uninitialized data in
the destination buffer.

NOT-FOR-MERGE: debug only

Link: https://syzkaller.appspot.com/bug?extid=d80abb5b890d39261e72
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 fs/hfsplus/bfind.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/hfsplus/bfind.c b/fs/hfsplus/bfind.c
index 336d654861c5..9b89dce00ee9 100644
--- a/fs/hfsplus/bfind.c
+++ b/fs/hfsplus/bfind.c
@@ -217,9 +217,19 @@ int hfs_brec_read(struct hfs_find_data *fd, void *rec, u32 rec_len)
 	res = hfs_brec_find(fd, hfs_find_rec_by_key);
 	if (res)
 		return res;
-	if (fd->entrylength > rec_len)
+	printk(KERN_ALERT "HFSPLUS_BREC_READ: rec_len=%u, fd->entrylength=%u\n",rec_len, fd->entrylength);
+	if (fd->entrylength > rec_len) {
+		printk(KERN_ALERT "HFSPLUS_BREC_READ: ERROR - entrylength > rec_len\n");
 		return -EINVAL;
+	}
+
+	if (fd->entrylength < rec_len) {
+		printk(KERN_ALERT "HFSPLUS_BREC_READ: WARNING - entrylength (%u) < rec_len (%u) - PARTIAL READ!\n",fd->entrylength, rec_len);
+	}
+
 	hfs_bnode_read(fd->bnode, rec, fd->entryoffset, fd->entrylength);
+
+	printk(KERN_ALERT "HFSPLUS_BREC_READ: Successfully read %u bytes (expected %u)\n",fd->entrylength, rec_len);
 	return 0;
 }
 
-- 
2.43.0