linux-kernel - [PATCH -next 2/2] smb3: fix potential wild-ptr-deref in 'smb3_free_compound

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Message-ID: <20221013071035.2890124-3-yebin10@huawei.com>
Date:   Thu, 13 Oct 2022 15:10:35 +0800
From:   Ye Bin <yebin10@...wei.com>
To:     <sfrench@...ba.org>, <pc@....nz>, <lsahlber@...hat.com>,
        <sprasad@...rosoft.com>, <linux-cifs@...r.kernel.org>
CC:     <samba-technical@...ts.samba.org>, <linux-kernel@...r.kernel.org>,
        <yebin10@...wei.com>
Subject: [PATCH -next 2/2] smb3: fix potential wild-ptr-deref in 'smb3_free_compound_rqst'

As 'smb3_init_transform_rq' first set 'new_rq[i].rq_npages', then
allocate page, if allocate page failed will call 'smb3_free_compound_rqst'
to free page. However, there may only allocate part of 'rq_npages' pages
which will lead to wild-ptr-deref when free pages.
To solve above issue just increase 'new_rq[i].rq_npages' after allocate
page success.

Signed-off-by: Ye Bin <yebin10@...wei.com>
---
 fs/cifs/smb2ops.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 180f0260cbc4..a1b47ce4ea15 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -4467,7 +4467,6 @@ smb3_init_transform_rq(struct TCP_Server_Info *server, int num_rqst,
 			goto err_free;
 
 		nrq->rq_pages = pages;
-		nrq->rq_npages = npages;
 		nrq->rq_offset = orq->rq_offset;
 		nrq->rq_pagesz = orq->rq_pagesz;
 		nrq->rq_tailsz = orq->rq_tailsz;
@@ -4480,6 +4479,7 @@ smb3_init_transform_rq(struct TCP_Server_Info *server, int num_rqst,
 			pages[j] = alloc_page(GFP_KERNEL|__GFP_HIGHMEM);
 			if (!pages[j])
 				goto err_free;
+			nrq->rq_npages++;
 		}
 
 		/* copy pages form the old */
-- 
2.31.1