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Fri, 04 Sep 2026 07:54:18 -0700 (PDT) Received: from dell-desktop ([2a02:587:4b5f:900:ef25:2f4:1792:4e6f]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-485885cb03asm6802799f8f.37.2026.09.04.07.54.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Sep 2026 07:54:17 -0700 (PDT) From: Anastasios Papagiannis To: bpf@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, akpm@linux-foundation.org, david@kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, kpsingh@kernel.org, matt@bobrowski.net, song@kernel.org, utilityemal77@gmail.com, sun.jian.kdev@gmail.com, tasos.papagiannnis@gmail.com Subject: [PATCH bpf-next v4 2/7] exec: Clear bprm->mm before dropping its reference Date: Fri, 4 Sep 2026 17:53:35 +0300 Message-ID: <20260904145340.40212-3-tasos.papagiannnis@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904145340.40212-1-tasos.papagiannnis@gmail.com> References: <20260904145340.40212-1-tasos.papagiannnis@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Once mmput() drops the final reference to bprm->mm, the pointer must no longer remain accessible through struct linux_binprm. The successful exec path and the bprm initialization error path already clear bprm->mm when ownership is transferred or released. Do the same in free_bprm() before calling mmput(). This is required for BPF kfuncs where bprm->mm is either NULL or points to a live mm_struct to ensure safe access. Signed-off-by: Anastasios Papagiannis Reviewed-by: Sun Jian --- fs/exec.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index a14f28b15607..4b4d8f0627a7 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1453,9 +1453,12 @@ void bprm_drop_loader(struct linux_binprm *bprm) static void free_bprm(struct linux_binprm *bprm) { - if (bprm->mm) { + struct mm_struct *mm = bprm->mm; + + if (mm) { acct_arg_size(bprm, 0); - mmput(bprm->mm); + bprm->mm = NULL; + mmput(mm); } if (bprm->user_ns) put_user_ns(bprm->user_ns); -- 2.55.0