From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 966D437F748; Thu, 17 Sep 2026 16:25:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789662305; cv=none; b=paOC4T01iyTqNt9Pe3boV57nDxFzXjwLSbkW8ZXD+EMtuDpB/zNexeysyjj0IwPCcSev+DtxFClT5DOJ3u45D4522A/czWw/cHSe5sersB+nqYzTXi9W4atPao6+e/Ut3WMiHA/C4Yo017W5bmVohi0ZjzNQPbgwaQcP4zrktnk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789662305; c=relaxed/simple; bh=StVNYANZU3sF8ij38este8h5c3k5S8te34QwspMLkvk=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=rFiafo1nM7dS521LuF00eiQEbtF1IilolA3LlmiIpqfHq7vbXxP6m9ugMNqmLFVr2yG378vprPlCaCKWpLFWtKuDS4fKbgDBCmGFfEp26JEwooWqkGMFc7hfgJWHMKCGoT6bv/3SGDp6Z5x2VB0QEyx0AO8mnBCf3UnaPV00doo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FKtFvH3J; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="FKtFvH3J" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 23A4F1F00893; Thu, 17 Sep 2026 16:24:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789662302; bh=smTxTWGKEevjb7CLSP8pWSf7Bj+6gdU3arnaSVDqSUY=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=FKtFvH3JVkLHGZsf8uYciO+eOgW72UaiAxrJ8Z6EShnCBvECEyuNVT6thNmFT//Ug WQBBkerWbn/RiCNB7oTGkWlzRoouZbpmeKKdGJmXI4vy6vcZC8qaF/vFREcBDK3wYa hFrcWKpaOhF1HX9ZAunYblSfjW+h3QPhjFVJ3fsvaxIME3zzaS4uDLtU1oV0f+NERU 3nrkCLxdf0q9p9vNtn5YcdtZBqIAxjROlfqBXEHoy1tKIZJgO4bmDwxfXFTAVXEks5 jyPqK4vfC+Du6aNYzuRmJowz/JEBr0ECvS1w0+K4eGzXH4K7D4xzRPlDlW4NO92MLu Q6Z9dtdwkL+1Q== From: "Lorenzo Stoakes (ARM)" Date: Thu, 17 Sep 2026 17:22:13 +0100 Subject: [PATCH v3 04/40] mm: consistently validate VMA state after mmap[_prepare] hooks Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260917-b4-mmap-prepare-vma-flag-sanify-v3-4-4583d8a23bca@kernel.org> References: <20260917-b4-mmap-prepare-vma-flag-sanify-v3-0-4583d8a23bca@kernel.org> In-Reply-To: <20260917-b4-mmap-prepare-vma-flag-sanify-v3-0-4583d8a23bca@kernel.org> To: Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , David Hildenbrand , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonathan Corbet , Greg Kroah-Hartman , Dennis Dalessandro , Jason Gunthorpe , Leon Romanovsky , Paul Moore , Stephen Smalley , Jaroslav Kysela , Takashi Iwai , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Doug Gilbert , "James E.J. Bottomley" , "Martin K. Petersen" , Jaya Kumar , Simona Vetter , Helge Deller , Sebastian Reichel , John Hubbard , Peter Xu , Masami Hiramatsu , Oleg Nesterov , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Rik van Riel , Harry Yoo , Juri Lelli , Vincent Guittot , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Arnd Bergmann , Muchun Song , Oscar Salvador , "Matthew Wilcox (Oracle)" , Jan Kara , Marc Zyngier , Oliver Upton , Catalin Marinas , Madhavan Srinivasan , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , "David S. Miller" , Andreas Larsson , Alexander Viro , Christian Brauner , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Youngjun Park , Johannes Weiner , Qi Zheng , Shakeel Butt , Axel Rasmussen , Yuanchu Xie , Wei Xu , Chengming Zhou , Michal Hocko , Miklos Szeredi , Xu Xin Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-usb@vger.kernel.org, linux-rdma@vger.kernel.org, selinux@vger.kernel.org, linux-sound@vger.kernel.org, bpf@vger.kernel.org, linux-scsi@vger.kernel.org, linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, fuse-devel@lists.linux.dev, "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=13137; i=ljs@kernel.org; h=from:subject:message-id; bh=StVNYANZU3sF8ij38este8h5c3k5S8te34QwspMLkvk=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLLWCO8XM/t45qrC/oPXV12s/t41ZbdVbN4rfdW5V7KlV RdHSG/l6ShlYRDjYpAVU2R5/kV8f5BI2LzOC/5uMHNYmUCGMHBxCsBEwrIY/vBq2GzI+3HJcc4u rW8uVzescW7OfCmQEqQ7K0Fa/8NJjlcM/wt2NZ371KRg+0p675Hnn3LmKpw3tnXtOZAreH23yoV geRYA X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 When the f_op->mmap_prepare or deprecated f_op->mmap hooks are invoked, the driver might have done something crazy that is not permitted by the kernel. Currently we check for three such cases in __mmap_new_file_vma(), but only if the legacy f_op->mmap hook is used: * Did sparc ADI result in invalid flags? * Did the driver alter vma->vm_start? * Did the driver make a file-backed mapping on a read-only file writable? Generalise these checks for both mmap_prepare and mmap and apply to all invocations of mmap_file(), the f_op->mmap and f_op->mmap_prepare handling in the core VMA code and the mmap_prepare compatibility layer. Also extend the vm_start check to vm_end also - drivers must not change the VMA range at all. We also WARN_ON_ONCE() on these conditions as they are things that should simply not occur in the kernel and it's important to call it out when it does. We invoke mmap_prepare_validate() after mmap_action_prepare(), as mmap actions often manipulate state in the descriptor thus providing the final state the VMA will be derived from. Also call mmap_validate_vma_flags() in insert_vm_struct() to ensure that special regions which are inserted (such as a VDSO or VVAR) also satisfy the sanity checks. This way every VMA established through an mmap hook, whether via mmap() or the compatibility layer, or inserted via insert_vm_struct(), has been validated. brk() VMAs never pass through a driver hook and so need no such check. While we're here, also fixup a couple disjoint blocks of #ifdef CONFIG_MMU. Finally, update the VMA userland tests to reflect the change. Signed-off-by: Lorenzo Stoakes (ARM) --- mm/internal.h | 51 ++++++++++++-------- mm/util.c | 19 ++++++-- mm/vma.c | 100 ++++++++++++++++++++++++++++++++++------ mm/vma.h | 25 ++++++++-- tools/testing/vma/include/dup.h | 10 ++++ 5 files changed, 163 insertions(+), 42 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index fe576d468af4..970fb34898b2 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -213,6 +213,24 @@ static inline void *folio_raw_mapping(const struct folio *folio) return (void *)(mapping & ~FOLIO_MAPPING_FLAGS); } +/* + * If the VMA has a close hook then close it, and since closing it might leave + * it in an inconsistent state which makes the use of any hooks suspect, clear + * them down by installing dummy empty hooks. + */ +static inline void vma_close(struct vm_area_struct *vma) +{ + if (vma->vm_ops && vma->vm_ops->close) { + vma->vm_ops->close(vma); + + /* + * The mapping is in an inconsistent state, and no further hooks + * may be invoked upon it. + */ + vma->vm_ops = &vma_dummy_vm_ops; + } +} + /* * This is a file-backed mapping, and is about to be memory mapped - invoke its * mmap hook and safely handle error conditions. On error, VMA hooks will be @@ -225,8 +243,12 @@ static inline void *folio_raw_mapping(const struct folio *folio) */ static inline int mmap_file(struct file *file, struct vm_area_struct *vma) { - int err = vfs_mmap(file, vma); + const unsigned long prev_start = vma->vm_start; + const unsigned long prev_end = vma->vm_end; + const vma_flags_t prev_flags = vma->flags; + int err; + err = vfs_mmap(file, vma); /* * Either we tried to call the file hook for mmap() and an error arose * or a driver set vma->vm_ops = NULL intending there to be no VMA @@ -239,26 +261,17 @@ static inline int mmap_file(struct file *file, struct vm_area_struct *vma) */ if (unlikely(err || !vma->vm_ops)) vma->vm_ops = &vma_dummy_vm_ops; + if (unlikely(err)) + return err; - return err; -} - -/* - * If the VMA has a close hook then close it, and since closing it might leave - * it in an inconsistent state which makes the use of any hooks suspect, clear - * them down by installing dummy empty hooks. - */ -static inline void vma_close(struct vm_area_struct *vma) -{ - if (vma->vm_ops && vma->vm_ops->close) { - vma->vm_ops->close(vma); - - /* - * The mapping is in an inconsistent state, and no further hooks - * may be invoked upon it. - */ - vma->vm_ops = &vma_dummy_vm_ops; + err = mmap_hook_validate(prev_start, prev_end, &prev_flags, vma); + if (unlikely(err)) { + vma->vm_start = prev_start; + vma->vm_end = prev_end; + vma_close(vma); } + + return err; } /* unmap_vmas is in mm/memory.c */ diff --git a/mm/util.c b/mm/util.c index 016932780925..bdd5923eebc7 100644 --- a/mm/util.c +++ b/mm/util.c @@ -1224,19 +1224,28 @@ EXPORT_SYMBOL(compat_set_desc_from_vma); int __compat_vma_mmap(struct vm_area_desc *desc, struct vm_area_struct *vma) { + struct vm_area_desc prev_desc; int err; + /* Derive state prior to mmap_prepare hook. */ + compat_set_desc_from_vma(&prev_desc, desc->file, vma); /* Perform any preparatory tasks for mmap action. */ err = mmap_action_prepare(desc); - if (err) { - if (desc->vm_file != vma->vm_file) - fput(desc->vm_file); - return err; - } + if (err) + goto err_put; + /* Check the caller did nothing crazy. */ + err = mmap_prepare_validate(&prev_desc, desc); + if (err) + goto err_put; /* Update the VMA from the descriptor. */ compat_set_vma_from_desc(vma, desc); /* Complete any specified mmap actions. */ return mmap_action_complete(vma, &desc->action, /*is_compat=*/true); + +err_put: + if (desc->vm_file != vma->vm_file) + fput(desc->vm_file); + return err; } EXPORT_SYMBOL(__compat_vma_mmap); diff --git a/mm/vma.c b/mm/vma.c index 05d2c676672e..d6ed10cefc8f 100644 --- a/mm/vma.c +++ b/mm/vma.c @@ -2623,16 +2623,6 @@ static int __mmap_new_file_vma(struct mmap_state *map, return error; } - /* Drivers cannot alter the address of the VMA. */ - WARN_ON_ONCE(map->addr != vma->vm_start); - /* - * Drivers should not permit writability when previously it was - * disallowed. - */ - VM_WARN_ON_ONCE(!vma_flags_same_pair(&map->vma_flags, &vma->flags) && - !vma_flags_test(&map->vma_flags, VMA_MAYWRITE_BIT) && - vma_test(vma, VMA_MAYWRITE_BIT)); - map->vma_flags = vma->flags; return 0; @@ -2710,11 +2700,6 @@ static int __mmap_new_vma(struct mmap_state *map, struct vm_area_struct **vmap, vma->flags = map->vma_flags; } -#ifdef CONFIG_SPARC64 - /* TODO: Fix SPARC ADI! */ - WARN_ON_ONCE(!arch_validate_flags(map->vm_flags)); -#endif - /* Lock the VMA since it is modified after insertion into VMA tree */ vma_start_write(vma); vma_iter_store_new(vmi, vma); @@ -2777,6 +2762,80 @@ static void __mmap_complete(struct mmap_state *map, struct vm_area_struct *vma) vma_set_page_prot(vma); } +/* Check to ensure that the VMA flags of a newly mapped VMA are sane. */ +static int mmap_validate_vma_flags(const vma_flags_t *flags) +{ +#ifdef CONFIG_SPARC64 + const vm_flags_t legacy_flags = vma_flags_to_legacy(*flags); + + /* TODO: Fix SPARC ADI! */ + if (WARN_ON_ONCE(!arch_validate_flags(legacy_flags))) + return -EINVAL; +#endif + + return 0; +} + +/* Check to ensure a driver hasn't done something crazy. */ +static int mmap_validate(unsigned long prev_start, unsigned long prev_end, + unsigned long curr_start, unsigned long curr_end, + const vma_flags_t *prev_flags, + const vma_flags_t *curr_flags) +{ + bool was_maywrite, is_maywrite; + + /* Drivers cannot alter the range of the VMA. */ + if (WARN_ON_ONCE(prev_start != curr_start || prev_end != curr_end)) + return -EINVAL; + + was_maywrite = vma_flags_test(prev_flags, VMA_MAYWRITE_BIT); + is_maywrite = vma_flags_test(curr_flags, VMA_MAYWRITE_BIT); + + /* A driver may not make a previously unwritable mapping writable. */ + if (WARN_ON_ONCE(!was_maywrite && is_maywrite)) + return -EINVAL; + + return mmap_validate_vma_flags(curr_flags); +} + +/** + * mmap_prepare_validate() - Ensure the driver hasn't violated invariants in its + * f_op->mmap_prepare hook. + * @prev_desc: The VMA descriptor prior to the mmap_prepare hook being called. + * @desc: The VMA descriptor after the mmap_prepare hook has been called. + * + * Returns: 0 on success, otherwise an error. + */ +int mmap_prepare_validate(const struct vm_area_desc *prev_desc, + const struct vm_area_desc *desc) +{ + return mmap_validate(prev_desc->start, prev_desc->end, + desc->start, desc->end, + &prev_desc->vma_flags, &desc->vma_flags); +} + +/** + * mmap_hook_validate() - Ensure the driver hasn't violated invariants in + * its f_op->mmap hook. + * @prev_start: The start of the mapping prior to the mmap hook. + * @prev_end: The end of the mapping prior to the mmap hook. + * @prev_flags: The VMA flags set for the VMA prior to the mmap hook. + * @vma: The VMA after the hook has been applied. + * + * Returns: 0 on success, otherwise an error. + */ +int mmap_hook_validate(unsigned long prev_start, unsigned long prev_end, + const vma_flags_t *prev_flags, + const struct vm_area_struct *vma) +{ + const unsigned long start = vma->vm_start; + const unsigned long end = vma->vm_end; + const vma_flags_t *flags = &vma->flags; + + return mmap_validate(prev_start, prev_end, start, end, prev_flags, + flags); +} + static int call_action_prepare(struct mmap_state *map, struct vm_area_desc *desc) { @@ -2803,6 +2862,7 @@ static int call_action_prepare(struct mmap_state *map, static int call_mmap_prepare(struct mmap_state *map, struct vm_area_desc *desc) { + const struct vm_area_desc prev_desc = *desc; int err; /* Invoke the hook. */ @@ -2822,6 +2882,11 @@ static int call_mmap_prepare(struct mmap_state *map, if (err) return err; + /* Check the caller did nothing crazy. */ + err = mmap_prepare_validate(&prev_desc, desc); + if (err) + return err; + /* Update fields permitted to be changed. */ map->pgoff = desc->pgoff; map->vma_flags = desc->vma_flags; @@ -3457,10 +3522,15 @@ int __vm_munmap(unsigned long start, size_t len, bool unlock) int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma) { unsigned long charged = vma_pages(vma); + int err; if (find_vma_intersection(mm, vma->vm_start, vma->vm_end)) return -ENOMEM; + err = mmap_validate_vma_flags(&vma->flags); + if (err) + return err; + if (vma_test(vma, VMA_ACCOUNT_BIT) && security_vm_enough_memory_mm(mm, charged)) return -ENOMEM; diff --git a/mm/vma.h b/mm/vma.h index f15faa83f3d6..b2c3bc832a48 100644 --- a/mm/vma.h +++ b/mm/vma.h @@ -782,14 +782,19 @@ struct vm_area_struct *vm_area_alloc(struct mm_struct *mm); struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig); void vm_area_free(struct vm_area_struct *vma); -/* vma_exec.c */ #ifdef CONFIG_MMU +int mmap_prepare_validate(const struct vm_area_desc *prev_desc, + const struct vm_area_desc *desc); + +int mmap_hook_validate(unsigned long prev_start, unsigned long prev_end, + const vma_flags_t *prev_flags, + const struct vm_area_struct *vma); + +/* vma_exec.c */ int create_init_stack_vma(struct mm_struct *mm, struct vm_area_struct **vmap, unsigned long *top_mem_p); int relocate_vma_down(struct vm_area_struct *vma, unsigned long shift); -#endif -#ifdef CONFIG_MMU /* * Denies creating a writable executable mapping or gaining executable permissions. * @@ -838,6 +843,20 @@ static inline bool map_deny_write_exec(const vma_flags_t *old, return false; } +#else +static inline int mmap_prepare_validate(const struct vm_area_desc *prev_desc, + const struct vm_area_desc *desc) +{ + return 0; +} + +static inline int mmap_hook_validate(unsigned long prev_start, + unsigned long prev_end, + const vma_flags_t *prev_flags, + const struct vm_area_struct *vma) +{ + return 0; +} #endif struct vm_area_struct *__install_special_mapping(struct mm_struct *mm, diff --git a/tools/testing/vma/include/dup.h b/tools/testing/vma/include/dup.h index 2fd422789717..2986ae6ca1e5 100644 --- a/tools/testing/vma/include/dup.h +++ b/tools/testing/vma/include/dup.h @@ -1359,13 +1359,23 @@ static inline int vfs_mmap_prepare(struct file *file, struct vm_area_desc *desc) return file->f_op->mmap_prepare(desc); } +int mmap_prepare_validate(const struct vm_area_desc *prev_desc, + const struct vm_area_desc *desc); + static inline int __compat_vma_mmap(struct vm_area_desc *desc, struct vm_area_struct *vma) { + struct vm_area_desc prev_desc; int err; + /* Derive state prior to mmap_prepare hook. */ + compat_set_desc_from_vma(&prev_desc, desc->file, vma); /* Perform any preparatory tasks for mmap action. */ err = mmap_action_prepare(desc); + if (err) + return err; + /* Check the caller did nothing crazy. */ + err = mmap_prepare_validate(&prev_desc, desc); if (err) return err; /* Update the VMA from the descriptor. */ -- 2.55.0