linux-kernel - [PATCH v2] smb: client: fix possible double free in smb2_set

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Message-Id: <20241015102036.2882322-1-suhui@nfschina.com>
Date: Tue, 15 Oct 2024 18:20:37 +0800
From: Su Hui <suhui@...china.com>
To: dan.carpenter@...aro.org,
	sfrench@...ba.org,
	pc@...guebit.com,
	ronniesahlberg@...il.com,
	sprasad@...rosoft.com,
	stfrench@...rosoft.com,
	tom@...pey.com,
	bharathsm@...rosoft.com,
	nathan@...nel.org,
	ndesaulniers@...gle.com,
	morbo@...gle.com,
	justinstitt@...gle.com
Cc: Su Hui <suhui@...china.com>,
	linux-cifs@...r.kernel.org,
	samba-technical@...ts.samba.org,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev,
	kernel-janitors@...r.kernel.org
Subject: [PATCH v2] smb: client: fix possible double free in smb2_set_ea()

Clang static checker(scan-build) warning：
fs/smb/client/smb2ops.c:1304:2: Attempt to free released memory.
 1304 |         kfree(ea);
      |         ^~~~~~~~~

There is a double free in such case:
'ea is initialized to NULL' -> 'first successful memory allocation for
ea' -> 'something failed, goto sea_exit' -> 'first memory release for ea'
-> 'goto replay_again' -> 'second goto sea_exit before allocate memory
for ea' -> 'second memory release for ea resulted in double free'.

Re-initialie 'ea' to NULL near to the replay_again label, it can fix this
double free problem.

Fixes: 4f1fffa23769 ("cifs: commands that are retried should have replay flag set")
Signed-off-by: Su Hui <suhui@...china.com>
---
v2: 
- Move 'ea = NULL' near to the replay_again label.(Dan's suggestion)

 fs/smb/client/smb2ops.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index 6b385fce3f2a..24a2aa04a108 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -1158,7 +1158,7 @@ smb2_set_ea(const unsigned int xid, struct cifs_tcon *tcon,
 	struct cifs_fid fid;
 	unsigned int size[1];
 	void *data[1];
-	struct smb2_file_full_ea_info *ea = NULL;
+	struct smb2_file_full_ea_info *ea;
 	struct smb2_query_info_rsp *rsp;
 	int rc, used_len = 0;
 	int retries = 0, cur_sleep = 1;
@@ -1179,6 +1179,7 @@ smb2_set_ea(const unsigned int xid, struct cifs_tcon *tcon,
 	if (!utf16_path)
 		return -ENOMEM;
 
+	ea = NULL;
 	resp_buftype[0] = resp_buftype[1] = resp_buftype[2] = CIFS_NO_BUFFER;
 	vars = kzalloc(sizeof(*vars), GFP_KERNEL);
 	if (!vars) {
-- 
2.30.2