| Message ID | 20181212220616.3918-1-lsahlber@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | cifs: check ntwrk_buf_start for NULL before dereferencing it | expand |
merged into cifs-2.6.git for-next On Wed, Dec 12, 2018 at 4:06 PM Ronnie Sahlberg <lsahlber@redhat.com> wrote: > > RHBZ: 1021460 > > There is an issue where when multiple threads open/close the same directory > ntwrk_buf_start might end up being NULL, causing the call to smbCalcSize > later to ops with a NULL deref. > > The real bug is why this happens and why this can become NULL for an > open cfile, which should not be allowed. > This patch tries to avoid a oops until the time when we fix the underlying > issue. > > Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com> > --- > fs/cifs/readdir.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c > index e169e1a5fd35..3925a7bfc74d 100644 > --- a/fs/cifs/readdir.c > +++ b/fs/cifs/readdir.c > @@ -655,7 +655,14 @@ find_cifs_entry(const unsigned int xid, struct cifs_tcon *tcon, loff_t pos, > /* scan and find it */ > int i; > char *cur_ent; > - char *end_of_smb = cfile->srch_inf.ntwrk_buf_start + > + char *end_of_smb; > + > + if (cfile->srch_inf.ntwrk_buf_start == NULL) { > + cifs_dbg(VFS, "ntwrk_buf_start is NULL during readdir\n"); > + return -EIO; > + } > + > + end_of_smb = cfile->srch_inf.ntwrk_buf_start + > server->ops->calc_smb_size( > cfile->srch_inf.ntwrk_buf_start, > server); > -- > 2.13.6 >
diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c index e169e1a5fd35..3925a7bfc74d 100644 --- a/fs/cifs/readdir.c +++ b/fs/cifs/readdir.c @@ -655,7 +655,14 @@ find_cifs_entry(const unsigned int xid, struct cifs_tcon *tcon, loff_t pos, /* scan and find it */ int i; char *cur_ent; - char *end_of_smb = cfile->srch_inf.ntwrk_buf_start + + char *end_of_smb; + + if (cfile->srch_inf.ntwrk_buf_start == NULL) { + cifs_dbg(VFS, "ntwrk_buf_start is NULL during readdir\n"); + return -EIO; + } + + end_of_smb = cfile->srch_inf.ntwrk_buf_start + server->ops->calc_smb_size( cfile->srch_inf.ntwrk_buf_start, server);
RHBZ: 1021460 There is an issue where when multiple threads open/close the same directory ntwrk_buf_start might end up being NULL, causing the call to smbCalcSize later to ops with a NULL deref. The real bug is why this happens and why this can become NULL for an open cfile, which should not be allowed. This patch tries to avoid a oops until the time when we fix the underlying issue. Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com> --- fs/cifs/readdir.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)