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

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Message-Id: <20241014113416.2280986-1-suhui@nfschina.com>
Date: Mon, 14 Oct 2024 19:34:17 +0800
From: Su Hui <suhui@...china.com>
To: 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] 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'.

Assign NULL value to 'ea' after 'kfree(ea)', 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>
---
 fs/smb/client/smb2ops.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index 6b385fce3f2a..5b42b352b703 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -1302,6 +1302,7 @@ smb2_set_ea(const unsigned int xid, struct cifs_tcon *tcon,
 
  sea_exit:
 	kfree(ea);
+	ea = NULL;
 	SMB2_open_free(&rqst[0]);
 	SMB2_set_info_free(&rqst[1]);
 	SMB2_close_free(&rqst[2]);
-- 
2.30.2