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Tue, 08 Sep 2026 06:53:39 -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, utilityemal77@gmail.com, viro@zeniv.linux.org.uk, tasos.papagiannnis@gmail.com Subject: [PATCH bpf-next v6 2/5] exec: Clear bprm->mm before dropping its reference Date: Tue, 8 Sep 2026 16:52:59 +0300 Message-ID: <20260908135302.74963-3-tasos.papagiannnis@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260908135302.74963-1-tasos.papagiannnis@gmail.com> References: <20260908135302.74963-1-tasos.papagiannnis@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 7094E40009 X-Stat-Signature: mdsnba73wur3y15zb9qkgy35sqjhe6d4 X-HE-Tag: 1788875621-43039 X-HE-Meta: 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 1UFBwOfb 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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