linux-kernel - [PATCH] fanotify: avoid possible NULL dereference

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Message-Id: <20230808091849.505809-1-suhui@nfschina.com>
Date:   Tue,  8 Aug 2023 17:18:50 +0800
From:   Su Hui <suhui@...china.com>
To:     jack@...e.cz, amir73il@...il.com, repnop@...gle.com
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org, Su Hui <suhui@...china.com>
Subject: [PATCH] fanotify: avoid possible NULL dereference

smatch error:
fs/notify/fanotify/fanotify_user.c:462 copy_fid_info_to_user():
we previously assumed 'fh' could be null (see line 421)

Fixes: afc894c784c8 ("fanotify: Store fanotify handles differently")
Signed-off-by: Su Hui <suhui@...china.com>
---
 fs/notify/fanotify/fanotify_user.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index f69c451018e3..5a5487ae2460 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -459,12 +459,13 @@ static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
 	if (WARN_ON_ONCE(len < sizeof(handle)))
 		return -EFAULT;
 
-	handle.handle_type = fh->type;
 	handle.handle_bytes = fh_len;
 
 	/* Mangle handle_type for bad file_handle */
 	if (!fh_len)
 		handle.handle_type = FILEID_INVALID;
+	else
+		handle.handle_type = fh->type;
 
 	if (copy_to_user(buf, &handle, sizeof(handle)))
 		return -EFAULT;
-- 
2.30.2