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Fri, 11 Sep 2026 16:33:45 +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 Ng/3GGktpGqJeQAAD6G6ig (envelope-from ); Fri, 11 Sep 2026 16:33:45 +0000 From: Gabriel Krisman Bertazi To: Jann Horn , Jens Axboe Cc: io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, Dominik Maier , stable+noautosel@kernel.org, Jann Horn Subject: Re: [PATCH] io_uring/fdinfo: ignore IORING_CQE_F_32 in last CQ array slot In-Reply-To: <20260911-uring-fdinfo-tighten-v1-1-47c62a154aca@google.com> Organization: SUSE References: <20260911-uring-fdinfo-tighten-v1-1-47c62a154aca@google.com> Date: Fri, 11 Sep 2026 13:33:42 -0300 Message-ID: <87y0d721eh.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-Spam-Score: -3.01 X-Rspamd-Queue-Id: 658F121D4C X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Level: X-Rspamd-Action: no action X-Spamd-Result: default: False [-3.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MISSING_XM_UA(0.00)[]; MIME_TRACE(0.00)[0:+]; HAS_ORG_HEADER(0.00)[]; TO_DN_SOME(0.00)[]; TAGGED_RCPT(0.00)[artist,noautosel]; RCVD_TLS_ALL(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_SEVEN(0.00)[7]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:email,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns]; 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]; DKIM_TRACE(0.00)[suse.de:+] X-Spam-Flag: NO Jann Horn writes: > > diff --git a/io_uring/fdinfo.c b/io_uring/fdinfo.c > index 3ae4804765b9..0b656a6c8428 100644 > --- a/io_uring/fdinfo.c > +++ b/io_uring/fdinfo.c > @@ -155,9 +155,11 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m) > for (i = 0; i < cq_entries; i++) { > struct io_uring_cqe *cqe; > bool cqe32 = false; > + bool is_last_cqarray_slot = (cq_head == cq_mask); > > cqe = &r->cqes[(cq_head & cq_mask)]; > - if (cqe->flags & IORING_CQE_F_32 || ctx->flags & IORING_SETUP_CQE32) > + if ((cqe->flags & IORING_CQE_F_32 || ctx->flags & IORING_SETUP_CQE32) && > + !is_last_cqarray_slot) Could we have a small comment here explaining we can't just trust IORING_CQE_F_32 for the last slot? it is very non-obvious to me from the code. Something as simple as (if I got it right): /* userspace can manipulate IORING_CQE_F_32 which is usually harmless, * except in the last CQ slot. Ignore the flag only for that slot to avoid * reading memory out-of-bounds. */ Either way, Reviewed-by: Gabriel Krisman Bertazi Thanks, > cqe32 = true; > seq_printf(m, "%5u: user_data:%llu, res:%d, flags:%x", > cq_head & cq_mask, cqe->user_data, cqe->res, > > --- > base-commit: 50d05c7c76c96b90462f24debacca971d2e86713 > change-id: 20260910-uring-fdinfo-tighten-1b1c18945305 > > Best regards, > -- > Jann Horn > -- Gabriel Krisman Bertazi