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fs/cifs/smb2pdu.c: fix buffer free in SMB2_ioctl_free 

The 2nd buffer could be NULL even if iov_len is not zero. This can
trigger a panic when handling symlinks. It's easy to reproduce with
LTP fs_racer scripts[1] which are randomly craete/delete/link files
and dirs. Fix this panic by checking if the 2nd buffer is padding
before kfree, like what we do in SMB2_open_free.

[1] https://github.com/linux-test-project/ltp/tree/master/testcases/kernel/fs/racer

Fixes: 2c87d6a94d ("cifs: Allocate memory for all iovs in smb2_ioctl")
Signed-off-by: Murphy Zhou <jencce.kernel@gmail.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Ronnie sahlberg <lsahlber@redhat.com>
This commit is contained in:
Murphy Zhou 2019-05-23 12:12:43 +08:00 committed by Steve French
parent 210782038b
commit 6457c20e33
1 changed files with 4 additions and 2 deletions
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6
fs/cifs/smb2pdu.c
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@ -2620,10 +2620,12 @@ SMB2_ioctl_init(struct cifs_tcon *tcon, struct smb_rqst *rqst,
void
SMB2_ioctl_free(struct smb_rqst *rqst)
{
int i;
if (rqst && rqst->rq_iov) {
cifs_small_buf_release(rqst->rq_iov[0].iov_base); /* request */
if (rqst->rq_iov[1].iov_len)
kfree(rqst->rq_iov[1].iov_base);
for (i = 1; i < rqst->rq_nvec; i++)
if (rqst->rq_iov[i].iov_base != smb2_padding)
kfree(rqst->rq_iov[i].iov_base);
}
}