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Thu, 22 Oct 2026 11:25:52 +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 7WbKBcDy2WrYZwAAD6G6ig (envelope-from ); Thu, 22 Oct 2026 11:25:52 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id AFD49A1417; Thu, 22 Oct 2026 13:25:51 +0200 (CEST) From: Jan Kara To: Christian Brauner Cc: , linux-aio@kvack.org, Jan Kara , Cheng Yongkang Subject: [PATCH] aio: avoid request count overflow in ioctx_alloc() Date: Thu, 22 Oct 2026 13:25:35 +0200 Message-ID: <20261022112534.3513745-2-jack@suse.cz> X-Mailer: git-send-email 2.51.0 X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1560; i=jack@suse.cz; h=from:subject; bh=YXJuss/QFH+2eSBPLJ4w2m5qq63mJV9zaIgSoyHXl7Y=; b=owEBbQGS/pANAwAIAZydqgc/ZEDZAcsmYgBq2fKugGKCNrv2VFXI3qchz5g676Qr5v+YOhq9d Ma57C9D0NyJATMEAAEIAB0WIQSrWdEr1p4yirVVKBycnaoHP2RA2QUCatnyrgAKCRCcnaoHP2RA 2THnB/9eOOdD3i1rCBraKR9Y5OW0ssHSIvDDDyKIOBPtYDK8lSMprtKJGgMSUvEcmTjj/q1C2aL UqzfvueWwEgkaPfzSJCweBdTNEJ31dQFU8sFneSW8TDvHGQRagqWal6vc/RT7rwQ4iMK37q+OAr pPn4wtxkERPwRhdXf7tTAsmUX5iGcMa8pzzrlYlTpSfmd3KDuObRVh8FOLxr+yhZ57xWiT/fYwy Zgm8gafG8uJ/e/OoCFMaBfakOYOglhZ2w/Mv6zj3pf2NRvQxWetkKWsqBb1cXsl2t33j/lwz62T i8hskVBnNipM46qcvpevhwsGfckrL/4kLfxddKn8Qqk+yNmi X-Developer-Key: i=jack@suse.cz; 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DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo]; RCVD_VIA_SMTP_AUTH(0.00)[]; FREEMAIL_CC(0.00)[vger.kernel.org,kvack.org,suse.cz,gmail.com]; DKIM_TRACE(0.00)[suse.cz:+]; RCPT_COUNT_FIVE(0.00)[5]; FREEMAIL_ENVRCPT(0.00)[gmail.com] X-Spam-Score: -12.01 ioctx_alloc() saves the 32-bit nr_events in max_reqs, then doubles nr_events before checking the ring-size bound. For nr_events=0x80000001, the doubled value wraps to 2, so the ring check passes and aio_setup_ring() builds a one-page/127-slot ring. The original 0x80000001 is still stored in ctx->max_reqs and charged to the global aio_nr quota. If an administrator has raised fs.aio-max-nr to at least 0x80000001, an unprivileged process can create that context and make later normal io_setup() calls fail with -EAGAIN until the wrapped context is destroyed. Check for too large number of requests before multiplying. Link: https://lore.kernel.org/all/20261022091748.3653127-1-teel4res@gmail.com Reported-by: Cheng Yongkang Signed-off-by: Jan Kara --- fs/aio.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index 4f32b45cb8a0..2086c0f263f6 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -805,13 +805,12 @@ static struct kioctx *ioctx_alloc(unsigned nr_events) * counters at a time, so make sure that isn't 0: */ nr_events = max(nr_events, num_possible_cpus() * 4); - nr_events *= 2; - /* Prevent overflows */ - if (nr_events > (0x10000000U / sizeof(struct io_event))) { + if (nr_events > (0x8000000U / sizeof(struct io_event))) { pr_debug("ENOMEM: nr_events too high\n"); return ERR_PTR(-EINVAL); } + nr_events *= 2; if (!nr_events || (unsigned long)max_reqs > aio_max_nr) return ERR_PTR(-EAGAIN); -- 2.51.0