From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lists.trustedfirmware.org (lists.trustedfirmware.org [18.214.241.189]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2DA0B606A32E for ; Thu, 5 Nov 2026 11:13:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.trustedfirmware.org header.i=@lists.trustedfirmware.org header.a=rsa-sha256 header.s=2024 header.b=RQX8U+Ek; dkim=fail reason="signature verification failed" (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=iJWzhgAC Received: from lists.trustedfirmware.org (localhost [127.0.0.1]) by lists.trustedfirmware.org (Postfix) with ESMTP id 8972F45479 for ; Thu, 5 Nov 2026 11:13:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=lists.trustedfirmware.org; s=2024; t=1793877222; bh=wmdqBY1Gfa1Mw6+QiBFfZqwGVpEY8UanncV+Jfoz3mk=; h=Subject:To:In-Reply-To:References:Date:CC:List-Id:List-Archive: List-Help:List-Owner:List-Post:List-Subscribe:List-Unsubscribe: From:Reply-To:From; b=RQX8U+EkMrrtQSz2tk71TMcjxfiHQW4Eusc2qKKyfogj4os0aDHYmFAquy2c22m4Y cdZXI8DeztqR48p/JXRvadJuXh/w+636G4fVCHM4Rchz8cL0ZwtvFkN47s5YIPgvP8 IxSLzb1cD4aNW+93JKsh3yFEmREgqR5trh/WrENIezpDpYOa3CTSxIoSA5r3PJtTkv gRLnVpg6ajFhdoufuTfs7bPmrySD9zcGwjXb+HL8UsbPbMWD31A+nZXF/xOdwN5ye8 s0oXjAZZrSm8n9OiEHeYKLTNKt/x/YrfgRN/n+Z18+lCnIs5n4jpK7b25RyaIQFCPK DkzSCTV2QzlEw== Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by lists.trustedfirmware.org (Postfix) with ESMTPS id 4C6F945497 for ; Thu, 5 Nov 2026 11:12:01 +0000 (UTC) Authentication-Results: lists.trustedfirmware.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=iJWzhgAC; dkim-atps=neutral Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id AEC4840431; Thu, 5 Nov 2026 11:12:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E12A91F00919; Thu, 5 Nov 2026 11:11:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793877120; bh=XYfDIMn9RzkoOerCRsuzNDWKhLeLvHeL9jAZyhrpQ1o=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=iJWzhgACqO8Oh3sg03HVyCjyDRqS/0Kt880riTR9yqMxOzYkEHCrqPSIFOkv9f/hh msR1KBHibiTLGBB9lFfczXDQTQIg7siuiS/H9s7ZO4h1RCevWVb/AkbQLYdz339fZ+ 5TOS+Z2LCW+KisR0sqsGOL8BDOM3Y3KdTqb2nOSAznmJYsxiGkPcnbh2Bw5HBAWtYy XP5SqcwLl3zSMCE7Y1FY9GWV9QwsTuYBPfhFQhYSuwSQSIgYrdqLB5w5SgLmMyxeK/ Mmjt52tv1l3Fg3yrRpcmpOMg9/ijrNbxtM7os5PorcJoiY10Lhz9Md+kpBwrSpxkYH aZg86Vo2dk+nA== Message-ID: Subject: Re: [PATCH v4 4/8] security: dma-buf: Add dma_buf_charge_task LSM hook To: "Albert Esteve" , "Tejun Heo" , "Johannes Weiner" , =?utf-8?b?TWljaGFsIEtvdXRuw70=?= , "Jonathan Corbet" , "Shuah Khan" , "Sumit Semwal" , =?utf-8?b?Q2hyaXN0aWFuIEvDtm5pZw==?= , "Michal Hocko" , "Roman Gushchin" , "Shakeel Butt" , "Muchun Song" , "Andrew Morton" , "Benjamin Gaignard" , "Brian Starkey" , "John Stultz" , "T.J. Mercier" , "Christian Brauner" , "Paul Moore" , "James Morris" , "Serge E. Hallyn" , "Stephen Smalley" , "Shuah Khan" , "Randy Dunlap" , =?utf-8?b?T25kcmVqIE1vc27DocSNZWs=?= , "Jens Wiklander" , "Sumit Garg" In-Reply-To: <20261104-v2_20230123_tjmercier_google_com-v4-4-1819a017000b@redhat.com> References: <20261104-v2_20230123_tjmercier_google_com-v4-0-1819a017000b@redhat.com> <20261104-v2_20230123_tjmercier_google_com-v4-4-1819a017000b@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Thu, 05 Nov 2026 11:11:58 +0000 X-Rspamd-Action: no action X-Spamd-Result: default: False [-5.50 / 15.00]; WHITELIST_SPF_DKIM(-3.00)[kernel.org:d:+,kernel.org:s:+]; BAYES_HAM(-3.00)[99.99%]; DWL_DNSWL_MED(-2.00)[kernel.org:dkim]; MISSING_MIME_VERSION(2.00)[]; SUSPICIOUS_RECIPS(1.50)[]; DMARC_POLICY_ALLOW(-0.50)[kernel.org,quarantine]; R_SPF_ALLOW(-0.20)[+ip4:172.234.252.31:c]; R_DKIM_ALLOW(-0.20)[kernel.org:s=k20260515]; MIME_GOOD(-0.10)[text/plain]; REPLYTO_DN_EQ_FROM_DN(0.00)[]; RCVD_TLS_LAST(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FREEMAIL_TO(0.00)[redhat.com,kernel.org,cmpxchg.org,suse.com,lwn.net,linuxfoundation.org,linaro.org,amd.com,linux.dev,linux-foundation.org,collabora.com,arm.com,google.com,paul-moore.com,namei.org,hallyn.com,gmail.com,infradead.org]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[33]; REPLYTO_DOM_NEQ_FROM_DOM(0.00)[]; DKIM_TRACE(0.00)[kernel.org:+]; REPLYTO_DOM_NEQ_TO_DOM(0.00)[]; DNSWL_BLOCKED(0.00)[172.234.252.31:from]; ALIAS_RESOLVED(0.00)[]; TO_MATCH_ENVRCPT_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_DN_SOME(0.00)[]; NEURAL_HAM(-0.00)[-1.000]; RCVD_VIA_SMTP_AUTH(0.00)[]; MISSING_XM_UA(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; FROM_NO_DN(0.00)[]; ASN(0.00)[asn:63949, ipnet:172.234.224.0/19, country:SG]; HAS_REPLYTO(0.00)[sashiko-reviews@lists.linux.dev] X-Rspamd-Server: lists.trustedfirmware.org X-Rspamd-Queue-Id: 4C6F945497 X-Spamd-Bar: ----- Message-ID-Hash: 7ENXGGSPNJMES3AHYAYSZ6W3NUUIB3XY X-Message-ID-Hash: 7ENXGGSPNJMES3AHYAYSZ6W3NUUIB3XY X-MailFrom: sashiko-bot@kernel.org X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-op-tee.lists.trustedfirmware.org-0; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: dri-devel@lists.freedesktop.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, op-tee@lists.trustedfirmware.org, media-ci@linuxtv.org X-Mailman-Version: 3.3.5 Precedence: list List-Id: Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: From: sashiko-bot--- via OP-TEE Reply-To: sashiko-reviews@lists.linux.dev, sashiko-bot@kernel.org X-Spam-Status: No, score=-11.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=unavailable autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 X-Archived-By: Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: - [High] mm: memcontrol: task cred and mm->owner mismatch in mem_cgroup_get= _from_fd() -- commit 8654d1fa67f56b32794f6b84163f6fcd4bd83d11 Author: Albert Esteve security: dma-buf: Add dma_buf_charge_task LSM hook This commit introduces the security_dma_buf_charge_task() LSM hook and calls it in mem_cgroup_get_from_fd() when resolving a target cgroup from a pidfd. > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 3e717b5663c82..dd276e1230cc4 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c [ ... ] > @@ -5698,6 +5701,14 @@ struct mem_cgroup *mem_cgroup_get_from_fd(int fd) > if (IS_ERR(task)) > return ERR_CAST(task); > =20 > + tcred =3D get_task_cred(task); > + ret =3D security_dma_buf_charge_task(current_cred(), tcred); > + put_cred(tcred); > + if (ret) { > + put_task_struct(task); > + return ERR_PTR(ret); > + } > + > mm =3D get_task_mm(task); > put_task_struct(task); > if (!mm) [Severity: High] As reported by Sashiko on v3 [1], in mem_cgroup_get_from_fd(), security_dma_buf_charge_task(current_cred(), tcred) checks the credentials = of task obtained via get_task_cred(task), while the charged mem_cgroup is then resolved indirectly via get_task_mm(task) and get_mem_cgroup_from_mm(mm): mm/memcontrol.c:get_mem_cgroup_from_mm() { rcu_read_lock(); do { memcg =3D mem_cgroup_from_task(rcu_dereference(mm->owner)); if (unlikely(!memcg)) memcg =3D root_mem_cgroup; } while (!css_tryget(&memcg->css)); rcu_read_unlock(); return memcg; } If task exits between get_task_mm(task) and get_mem_cgroup_from_mm(mm), exit_mm() clears task->mm and calls mm_update_next_owner(mm), which sees mm_users > 1 with no live task using mm and sets mm->owner to NULL: kernel/exit.c:mm_update_next_owner() { ... WRITE_ONCE(mm->owner, NULL); ... } In that case, get_mem_cgroup_from_mm(mm) falls back to returning root_mem_cgroup, where try_charge() skips accounting because mem_cgroup_is_root(memcg) is true. Could a confined process fork a short-lived helper child with matching credentials to pass security_dma_buf_charge_task() and race its exit to charge or transfer dma-buf allocations to root_mem_cgroup, escaping its cgroup memory limit? Similarly, if task shares an mm_struct with another task via clone(CLONE_VM) that has different credentials or cgroup membership, mm->owner may not be task. Could security_dma_buf_charge_task() validate task's credentials while get_mem_cgroup_from_mm(mm) charges the cgroup of a different mm->owner task? [1] https://lore.kernel.org/r/20261027-v2_20230123_tjmercier_google_com-v3-= 3-78d2c4cb8647@redhat.com --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261104-v2_2023012= 3_tjmercier_google_com-v4-0-1819a017000b@redhat.com?part=3D4