From: Steve French <smfrench@gmail.com>
To: Shyam Prasad N <nspmangalore@gmail.com>
Cc: Henrique Carvalho <henrique.carvalho@suse.com>,
pc@manguebit.org, ronniesahlberg@gmail.com,
sprasad@microsoft.com, tom@talpey.com, bharathsm@microsoft.com,
ematsumiya@suse.de, linux-cifs@vger.kernel.org
Subject: Re: [PATCH] smb: client: fix potential cfid UAF in smb2_query_info_compound
Date: Tue, 28 Oct 2025 08:43:54 -0500 [thread overview]
Message-ID: <CAH2r5msT3tWaFXTGNhLMZDobZ7f=uKeNZQH3QfJ=WaR1srz43A@mail.gmail.com> (raw)
In-Reply-To: <CANT5p=qooR0ieHbtuG0APbJvF7+F6o7ZMHtezm40kiEWTs+oaw@mail.gmail.com>
On Tue, Oct 28, 2025 at 1:02 AM Shyam Prasad N <nspmangalore@gmail.com> wrote:
>
> On Tue, Oct 28, 2025 at 6:03 AM Steve French <smfrench@gmail.com> wrote:
> >
> > merged into cifs-2.6.git for-next pending testing
> >
> > On Mon, Oct 27, 2025 at 4:31 PM Henrique Carvalho
> > <henrique.carvalho@suse.com> wrote:
> > >
> > > When smb2_query_info_compound() retries, a previously allocated cfid may
> > > have been freed in the first attempt.
> > > Because cfid wasn't reset on replay, later cleanup could act on a stale
> > > pointer, leading to a potential use-after-free.
> > >
> > > Reinitialize cfid to NULL under the replay label.
> > >
> > > Example trace (trimmed):
> > >
> > > refcount_t: underflow; use-after-free.
> > > WARNING: CPU: 1 PID: 11224 at ../lib/refcount.c:28 refcount_warn_saturate+0x9c/0x110
> > > [...]
> > > RIP: 0010:refcount_warn_saturate+0x9c/0x110
> > > [...]
> > > Call Trace:
> > > <TASK>
> > > smb2_query_info_compound+0x29c/0x5c0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]
> > > ? step_into+0x10d/0x690
> > > ? __legitimize_path+0x28/0x60
> > > smb2_queryfs+0x6a/0xf0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]
> > > smb311_queryfs+0x12d/0x140 [cifs f90b72658819bd21c94769b6a652029a07a7172f]
> > > ? kmem_cache_alloc+0x18a/0x340
> > > ? getname_flags+0x46/0x1e0
> > > cifs_statfs+0x9f/0x2b0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]
> > > statfs_by_dentry+0x67/0x90
> > > vfs_statfs+0x16/0xd0
> > > user_statfs+0x54/0xa0
> > > __do_sys_statfs+0x20/0x50
> > > do_syscall_64+0x58/0x80
> > >
> > > Fixes: 4f1fffa237692 ("cifs: commands that are retried should have replay flag set")
> > > Reviewed-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
> > > Reviewed-by: Enzo Matsumiya <ematsumiya@suse.de>
> > > Signed-off-by: Henrique Carvalho <henrique.carvalho@suse.com>
> > > ---
> > > fs/smb/client/smb2ops.c | 3 ++-
> > > 1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
> > > index 0f9130ef2e7d..1e39f2165e42 100644
> > > --- a/fs/smb/client/smb2ops.c
> > > +++ b/fs/smb/client/smb2ops.c
> > > @@ -2799,11 +2799,12 @@ smb2_query_info_compound(const unsigned int xid, struct cifs_tcon *tcon,
> > > struct cifs_fid fid;
> > > int rc;
> > > __le16 *utf16_path;
> > > - struct cached_fid *cfid = NULL;
> > > + struct cached_fid *cfid;
> > > int retries = 0, cur_sleep = 1;
> > >
> > > replay_again:
> > > /* reinitialize for possible replay */
> > > + cfid = NULL;
> > > flags = CIFS_CP_CREATE_CLOSE_OP;
> > > oplock = SMB2_OPLOCK_LEVEL_NONE;
> > > server = cifs_pick_channel(ses);
> > > --
> > > 2.50.1
> > >
> > >
> >
> >
> > --
> > Thanks,
> >
> > Steve
> >
>
> Thanks. Looks good to me. Should CC stable.
Done. updated to add Cc: stable and Acked-by
--
Thanks,
Steve
prev parent reply other threads:[~2025-10-28 13:44 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-27 21:29 [PATCH] smb: client: fix potential cfid UAF in smb2_query_info_compound Henrique Carvalho
2025-10-28 0:32 ` Steve French
2025-10-28 6:02 ` Shyam Prasad N
2025-10-28 13:43 ` Steve French [this message]
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