From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 596418C08 for ; Wed, 24 Jan 2024 10:17:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706091430; cv=none; b=J2DwstDz2AsFx10k5DQuxoZRyrUuluu5nvsFZbmyn+Fo3xjqetArvtNUB+lul5asYzL2T5h5EJG+uJ2JXS62ChxkfylRV9oHaZ2sjF84zQm2a9R0Wao3CruhXrL1Wa2YEcjzCAR1w/vSHINxvCqM8LEsdpLMD+zXiRpPE6UtelU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706091430; c=relaxed/simple; bh=jdPXvL9uwjQg+I/Tp1HtUrD+IBx+K3pLirPHMriVCr8=; h=Date:To:From:Subject:Message-Id; b=lD5+DIAi0QPxfSwUEBGo3aonq/ai+TNKHTMwLL1vfCjtMWF86kHwwKpgvPR0MqDfrBehGaq2NTzkS6Cuc58HiC2q0s9FBDZrT3Gq8OyKC1g1hOuMaaNA4MXrYC/ojB9Z3Sjoaj3lSqfcwU3jMtMFT6Pq8UPBuy4rKOESVYV4hNQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=PW5RVn8e; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="PW5RVn8e" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 07AB2C43394; Wed, 24 Jan 2024 10:17:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1706091429; bh=jdPXvL9uwjQg+I/Tp1HtUrD+IBx+K3pLirPHMriVCr8=; h=Date:To:From:Subject:From; b=PW5RVn8efH16AGqDBA1lDv1fmVam3LlQle6Ujo9xMYS3fy5nWB55KYLQHOTeb09Ty 9XeSztFRHifN1YqyGt7y7mbkVLHmo6RqKN9AwzNLVFMqTzDMTdQwMGeyvEb2dHIM51 iyChsLW1EcUtzGRJYw06GadtUv6JQNdIYztiqwNw= Date: Wed, 24 Jan 2024 02:17:07 -0800 To: mm-commits@vger.kernel.org,yuzhao@google.com,yangxingui@huawei.com,willy@infradead.org,wangkefeng.wang@huawei.com,vishal.moola@gmail.com,viro@zeniv.linux.org.uk,vbabka@suse.cz,usama.anjum@collabora.com,talumbau@google.com,sj@kernel.org,sidhartha.kumar@oracle.com,ryan.roberts@arm.com,peterx@redhat.com,paulmck@kernel.org,mgorman@techsingularity.net,mathieu.desnoyers@efficios.com,lstoakes@gmail.com,Liam.Howlett@oracle.com,keescook@chromium.org,jhubbard@nvidia.com,jgg@ziepe.ca,jack@suse.cz,hughd@google.com,dhowells@redhat.com,dchinner@redhat.com,david@redhat.com,casey@schaufler-ca.com,brauner@kernel.org,ben.wolsieffer@hefring.com,axelrasmussen@google.com,avagin@google.com,andriy.shevchenko@linux.intel.com,surenb@google.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-make-vm_area_struct-anon_name-field-rcu-safe.patch added to mm-unstable branch Message-Id: <20240124101709.07AB2C43394@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm: make vm_area_struct anon_name field RCU-safe has been added to the -mm mm-unstable branch. Its filename is mm-make-vm_area_struct-anon_name-field-rcu-safe.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-make-vm_area_struct-anon_name-field-rcu-safe.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Suren Baghdasaryan Subject: mm: make vm_area_struct anon_name field RCU-safe Date: Tue, 23 Jan 2024 15:10:12 -0800 For lockless /proc/pid/maps reading we have to ensure all the fields used when generating the output are RCU-safe. The only pointer fields in vm_area_struct which are used to generate that file's output are vm_file and anon_name. vm_file is RCU-safe but anon_name is not. Make anon_name RCU-safe as well. Link: https://lkml.kernel.org/r/20240123231014.3801041-1-surenb@google.com Signed-off-by: Suren Baghdasaryan Cc: Al Viro Cc: Andrei Vagin Cc: Andy Shevchenko Cc: Axel Rasmussen Cc: Ben Wolsieffer Cc: Casey Schaufler Cc: Christian Brauner Cc: Dave Chinner Cc: David Hildenbrand Cc: David Howells Cc: Hugh Dickins Cc: Jan Kara Cc: Jason Gunthorpe Cc: John Hubbard Cc: Kees Cook Cc: Kefeng Wang Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Mathieu Desnoyers Cc: Matthew Wilcox (Oracle) Cc: Mel Gorman Cc: Muhammad Usama Anjum Cc: Paul E. McKenney Cc: Peter Xu Cc: Ryan Roberts Cc: SeongJae Park Cc: Sidhartha Kumar Cc: T.J. Alumbaugh Cc: Vishal Moola (Oracle) Cc: Vlastimil Babka Cc: Xingui Yang Cc: Yu Zhao Signed-off-by: Andrew Morton --- include/linux/mm_inline.h | 10 +++++++++- include/linux/mm_types.h | 3 ++- mm/madvise.c | 30 ++++++++++++++++++++++++++---- 3 files changed, 37 insertions(+), 6 deletions(-) --- a/include/linux/mm_inline.h~mm-make-vm_area_struct-anon_name-field-rcu-safe +++ a/include/linux/mm_inline.h @@ -389,7 +389,7 @@ static inline void dup_anon_vma_name(str struct anon_vma_name *anon_name = anon_vma_name(orig_vma); if (anon_name) - new_vma->anon_name = anon_vma_name_reuse(anon_name); + rcu_assign_pointer(new_vma->anon_name, anon_vma_name_reuse(anon_name)); } static inline void free_anon_vma_name(struct vm_area_struct *vma) @@ -411,6 +411,8 @@ static inline bool anon_vma_name_eq(stru !strcmp(anon_name1->name, anon_name2->name); } +struct anon_vma_name *anon_vma_name_get_rcu(struct vm_area_struct *vma); + #else /* CONFIG_ANON_VMA_NAME */ static inline void anon_vma_name_get(struct anon_vma_name *anon_name) {} static inline void anon_vma_name_put(struct anon_vma_name *anon_name) {} @@ -424,6 +426,12 @@ static inline bool anon_vma_name_eq(stru return true; } +static inline +struct anon_vma_name *anon_vma_name_get_rcu(struct vm_area_struct *vma) +{ + return NULL; +} + #endif /* CONFIG_ANON_VMA_NAME */ static inline void init_tlb_flush_pending(struct mm_struct *mm) --- a/include/linux/mm_types.h~mm-make-vm_area_struct-anon_name-field-rcu-safe +++ a/include/linux/mm_types.h @@ -545,6 +545,7 @@ struct vm_userfaultfd_ctx {}; struct anon_vma_name { struct kref kref; + struct rcu_head rcu; /* The name needs to be at the end because it is dynamically sized. */ char name[]; }; @@ -699,7 +700,7 @@ struct vm_area_struct { * terminated string containing the name given to the vma, or NULL if * unnamed. Serialized by mmap_lock. Use anon_vma_name to access. */ - struct anon_vma_name *anon_name; + struct anon_vma_name __rcu *anon_name; #endif #ifdef CONFIG_SWAP atomic_long_t swap_readahead_info; --- a/mm/madvise.c~mm-make-vm_area_struct-anon_name-field-rcu-safe +++ a/mm/madvise.c @@ -88,14 +88,15 @@ void anon_vma_name_free(struct kref *kre { struct anon_vma_name *anon_name = container_of(kref, struct anon_vma_name, kref); - kfree(anon_name); + kfree_rcu(anon_name, rcu); } struct anon_vma_name *anon_vma_name(struct vm_area_struct *vma) { mmap_assert_locked(vma->vm_mm); - return vma->anon_name; + return rcu_dereference_protected(vma->anon_name, + rwsem_is_locked(&vma->vm_mm->mmap_lock)); } /* mmap_lock should be write-locked */ @@ -105,7 +106,7 @@ static int replace_anon_vma_name(struct struct anon_vma_name *orig_name = anon_vma_name(vma); if (!anon_name) { - vma->anon_name = NULL; + rcu_assign_pointer(vma->anon_name, NULL); anon_vma_name_put(orig_name); return 0; } @@ -113,11 +114,32 @@ static int replace_anon_vma_name(struct if (anon_vma_name_eq(orig_name, anon_name)) return 0; - vma->anon_name = anon_vma_name_reuse(anon_name); + rcu_assign_pointer(vma->anon_name, anon_vma_name_reuse(anon_name)); anon_vma_name_put(orig_name); return 0; } + +/* + * Returned anon_vma_name is stable due to elevated refcount but not guaranteed + * to be assigned to the original VMA after the call. + */ +struct anon_vma_name *anon_vma_name_get_rcu(struct vm_area_struct *vma) +{ + struct anon_vma_name __rcu *anon_name; + + WARN_ON_ONCE(!rcu_read_lock_held()); + + anon_name = rcu_dereference(vma->anon_name); + if (!anon_name) + return NULL; + + if (unlikely(!kref_get_unless_zero(&anon_name->kref))) + return NULL; + + return anon_name; +} + #else /* CONFIG_ANON_VMA_NAME */ static int replace_anon_vma_name(struct vm_area_struct *vma, struct anon_vma_name *anon_name) _ Patches currently in -mm which might be from surenb@google.com are mm-make-vm_area_struct-anon_name-field-rcu-safe.patch mm-add-mm_struct-sequence-number-to-detect-write-locks.patch mm-maps-read-proc-pid-maps-under-rcu.patch