From: Steve French <smfrench@gmail.com>
To: Henrique Carvalho <henrique.carvalho@suse.com>
Cc: 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: Mon, 27 Oct 2025 19:32:59 -0500 [thread overview]
Message-ID: <CAH2r5mszqYAxcvuQp+VXMqx1OA--KvqNAXzX0nQN1BeDg6hFJg@mail.gmail.com> (raw)
In-Reply-To: <20251027212919.2082212-1-henrique.carvalho@suse.com>
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
next prev parent reply other threads:[~2025-10-28 0:33 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 [this message]
2025-10-28 6:02 ` Shyam Prasad N
2025-10-28 13:43 ` Steve French
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