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cifs: Fix use-after-free in SMB2_read

There is a KASAN use-after-free:
BUG: KASAN: use-after-free in SMB2_read+0x1136/0x1190
Read of size 8 at addr ffff8880b4e45e50 by task ln/1009

Should not release the 'req' because it will use in the trace.

Fixes: eccb442 ("smb3: Add ftrace tracepoints for improved SMB3 debugging")

Signed-off-by: ZhangXiaoxu <>
Signed-off-by: Steve French <>
CC: Stable <> 4.18+
Reviewed-by: Pavel Shilovsky <>
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z00467499 authored and Steve French committed Apr 6, 2019
1 parent 6a3eb33 commit 088aaf17aa79300cab14dbee2569c58cfafd7d6e
Showing with 2 additions and 2 deletions.
  1. +2 −2 fs/cifs/smb2pdu.c
@@ -3448,8 +3448,6 @@ SMB2_read(const unsigned int xid, struct cifs_io_parms *io_parms,
rqst.rq_nvec = 1;

rc = cifs_send_recv(xid, ses, &rqst, &resp_buftype, flags, &rsp_iov);

rsp = (struct smb2_read_rsp *)rsp_iov.iov_base;

if (rc) {
@@ -3471,6 +3469,8 @@ SMB2_read(const unsigned int xid, struct cifs_io_parms *io_parms,
io_parms->tcon->tid, ses->Suid,
io_parms->offset, io_parms->length);


*nbytes = le32_to_cpu(rsp->DataLength);
if ((*nbytes > CIFS_MAX_MSGSIZE) ||
(*nbytes > io_parms->length)) {

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