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Mon, 07 Sep 2026 09:52:57 -0700 (PDT) From: Anastasios Papagiannis To: bpf@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, david@kernel.org, akpm@linux-foundation.org, andrii@kernel.org, ast@kernel.org, brauner@kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, kpsingh@kernel.org, ljs@kernel.org, matt@bobrowski.net, memxor@gmail.com, song@kernel.org, sun.jian.kdev@gmail.com, tasos.papagiannnis@gmail.com, utilityemal77@gmail.com, viro@zeniv.linux.org.uk Subject: [PATCH bpf-next v5 2/7] exec: Clear bprm->mm before dropping its reference Date: Mon, 7 Sep 2026 19:52:15 +0300 Message-ID: <20260907165220.52431-3-tasos.papagiannnis@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260907165220.52431-1-tasos.papagiannnis@gmail.com> References: <20260907165220.52431-1-tasos.papagiannnis@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: h9swwhpfr6n5aaaeakatjjcxh5zyg84h X-Rspamd-Queue-Id: 3AFCF180005 X-Rspamd-Server: rspam06 X-HE-Tag: 1788799980-14289 X-HE-Meta: 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 HfKNlxDN 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 745f6eb5279e..4ddd403fd91c 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1456,9 +1456,12 @@ 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