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Mon, 24 Aug 2026 13:24:04 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id p8aSBvRFjGrXVgAAD6G6ig (envelope-from ); Mon, 24 Aug 2026 13:24:04 +0000 From: Gabriel Krisman Bertazi To: Laxman Acharya , Jens Axboe Cc: Pavel Begunkov , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, Laxman Acharya Padhya , stable@vger.kernel.org Subject: Re: [PATCH] io_uring/query: cap user size passed to copy_struct_to_user In-Reply-To: <20260821103317.91437-1-acharyalaxman8848@gmail.com> Organization: SUSE References: <20260821103317.91437-1-acharyalaxman8848@gmail.com> Date: Mon, 24 Aug 2026 09:24:01 -0400 Message-ID: <87wltfslce.fsf@mailhost.krisman.be> Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[99.99%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; ARC_NA(0.00)[]; HAS_ORG_HEADER(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_ALL(0.00)[]; TO_DN_SOME(0.00)[]; TAGGED_RCPT(0.00)[]; RCPT_COUNT_SEVEN(0.00)[7]; MISSING_XM_UA(0.00)[]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[gmail.com,vger.kernel.org]; FREEMAIL_TO(0.00)[gmail.com,kernel.dk]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.de:email] X-Spam-Flag: NO X-Spam-Score: -2.80 X-Spam-Level: Laxman Acharya writes: > From: Laxman Acharya Padhya > > io_handle_query_entry() clamps hdr.size for the inbound copy_from_user() > but keeps the original user value as usize. copy_struct_to_user() uses > that usize and, when it is larger than the kernel result, clear_user()s > the trailing bytes. > > As hdr.size is a __u32, a query can request nearly 4 GiB of zeroing, > including on the error path where res_size stays 0. The interface is > reachable without a ring via IORING_REGISTER_QUERY. > > Reject sizes larger than PAGE_SIZE, as recommended for copy_struct_* > interfaces. > > Fixes: c265ae75f900 ("io_uring: introduce io_uring querying") > Cc: stable@vger.kernel.org # 6.18+ > Signed-off-by: Laxman Acharya Padhya Looks good. feel free to add: Reviewed-by: Gabriel Krisman Bertazi > --- > io_uring/query.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/io_uring/query.c b/io_uring/query.c > index 88a325736992..f2b5e19e5af6 100644 > --- a/io_uring/query.c > +++ b/io_uring/query.c > @@ -76,6 +76,9 @@ static int io_handle_query_entry(union io_query_data *data, void __user *uhdr, > > if (copy_from_user(&hdr, uhdr, sizeof(hdr))) > return -EFAULT; > + /* copy_struct_to_user() zeros up to usize bytes */ > + if (hdr.size > PAGE_SIZE) > + return -E2BIG; > usize = hdr.size; > hdr.size = min(hdr.size, IO_MAX_QUERY_SIZE); > udata = u64_to_user_ptr(hdr.query_data); > -- > 2.51.2 -- Gabriel Krisman Bertazi