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Howlett" , Vlastimil Babka , Jann Horn , linux-mm@kvack.org, Peng Zhang Subject: Re: [PATCH] fork: avoid inappropriate uprobe access to invalid mm Message-ID: <20241210172315.GC31266@redhat.com> References: <20241210163104.55181-1-lorenzo.stoakes@oracle.com> <20241210165334.GB31266@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241210165334.GB31266@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Rspamd-Queue-Id: 599651C0002 X-Stat-Signature: z7b9zaznzjezj41zp6o3y6gbsfwb4m63 X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1733851402-556792 X-HE-Meta: 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 UifQ7wsv 5kbGrMMbT518xuyaXvGOOPHZTAQ86xr78YjJWYdbnO5DQenClRP/n6thC9zffwJBKzCwUrCo6comb/9bZdd8D1cizK/GkShKigfa1lELQDgUhN43lTxqVllbFbzgf9ecd6UI587hjIGSOPyGsL5+vdKycCZ9wZqc7WKHoWOUnCfy9Kq9yC9Q+wUFV2vJuk7e5Rnz0TVLDMmZvZ1AWd7sr6R4H28ZJKur1xMgeRDLG0fJkb32m51INOCzCZw2/HY7PKbrA6hMOmz13Xr7r/UFwTP3qsrugC4iSqm1VOhlm4KN6asbOOL7X2n/mUw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.003489, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 12/10, Oleg Nesterov wrote: > > I must have missed something, but... > > On 12/10, Lorenzo Stoakes wrote: > > > > @@ -1746,9 +1741,11 @@ static struct mm_struct *dup_mm(struct task_struct *tsk, > > if (!mm_init(mm, tsk, mm->user_ns)) > > goto fail_nomem; > > > > + uprobe_start_dup_mmap(); > > err = dup_mmap(mm, oldmm); > > if (err) > > - goto free_pt; > > + goto free_pt_end_uprobe; > > + uprobe_end_dup_mmap(); > > > > mm->hiwater_rss = get_mm_rss(mm); > > mm->hiwater_vm = mm->total_vm; > > @@ -1758,6 +1755,8 @@ static struct mm_struct *dup_mm(struct task_struct *tsk, > > > > return mm; > > > > +free_pt_end_uprobe: > > + uprobe_end_dup_mmap(); > > if dup_mmap() fails and "mm" is incomplete, then with this version dup_mmap_sem > is dropped before __mmput/exit_mmap/etc. How can this help? Easy to fix, but what ensures that another mmget(mm) is not possible until dup_mm() calls mmput() and drops dup_mmap_sem? Sorry, my understanding of mm/ is very limited... Oleg.