From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Yznaga Subject: Re: [RFC PATCH 3/5] mm: introduce VM_EXEC_KEEP Date: Wed, 29 Jul 2020 16:20:32 -0700 Message-ID: References: <1595869887-23307-1-git-send-email-anthony.yznaga@oracle.com> <1595869887-23307-4-git-send-email-anthony.yznaga@oracle.com> <20200729135211.zodforvnv2xvdchm@box> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Received: from userp2120.oracle.com ([156.151.31.85]:33794 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726876AbgG2XVt (ORCPT ); Wed, 29 Jul 2020 19:21:49 -0400 In-Reply-To: <20200729135211.zodforvnv2xvdchm@box> Content-Language: en-US Sender: linux-arch-owner@vger.kernel.org List-ID: To: "Kirill A. Shutemov" Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, mhocko@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, arnd@arndb.de, ebiederm@xmission.com, keescook@chromium.org, gerg@linux-m68k.org, ktkhai@virtuozzo.com, christian.brauner@ubuntu.com, peterz@infradead.org, esyr@redhat.com, jgg@ziepe.ca, christian@kellner.me, areber@redhat.com, cyphar@cyphar.com, steven.sistare@oracle.com On 7/29/20 6:52 AM, Kirill A. Shutemov wrote: > On Mon, Jul 27, 2020 at 10:11:25AM -0700, Anthony Yznaga wrote: >> A vma with the VM_EXEC_KEEP flag is preserved across exec. For anonymous >> vmas only. For safety, overlap with fixed address VMAs created in the new >> mm during exec (e.g. the stack and elf load segments) is not permitted and >> will cause the exec to fail. >> (We are studying how to guarantee there are no conflicts. Comments welcome.) >> >> Signed-off-by: Steve Sistare >> Signed-off-by: Anthony Yznaga >> --- >> arch/x86/Kconfig | 1 + >> fs/exec.c | 20 ++++++++++++++++++++ >> include/linux/mm.h | 5 +++++ >> kernel/fork.c | 2 +- >> mm/mmap.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++ >> 5 files changed, 74 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >> index 883da0abf779..fc36eb2f45c0 100644 >> --- a/arch/x86/Kconfig >> +++ b/arch/x86/Kconfig >> @@ -30,6 +30,7 @@ config X86_64 >> select MODULES_USE_ELF_RELA >> select NEED_DMA_MAP_STATE >> select SWIOTLB >> + select ARCH_USES_HIGH_VMA_FLAGS >> >> config FORCE_DYNAMIC_FTRACE >> def_bool y >> diff --git a/fs/exec.c b/fs/exec.c >> index 262112e5f9f8..1de09c4eef00 100644 >> --- a/fs/exec.c >> +++ b/fs/exec.c >> @@ -1069,6 +1069,20 @@ ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len) >> EXPORT_SYMBOL(read_code); >> #endif >> >> +static int vma_dup_some(struct mm_struct *old_mm, struct mm_struct *new_mm) >> +{ >> + struct vm_area_struct *vma; >> + int ret; >> + >> + for (vma = old_mm->mmap; vma; vma = vma->vm_next) >> + if (vma->vm_flags & VM_EXEC_KEEP) { >> + ret = vma_dup(vma, new_mm); >> + if (ret) >> + return ret; >> + } >> + return 0; >> +} >> + >> /* >> * Maps the mm_struct mm into the current task struct. >> * On success, this function returns with the mutex >> @@ -1104,6 +1118,12 @@ static int exec_mmap(struct mm_struct *mm) >> mutex_unlock(&tsk->signal->exec_update_mutex); >> return -EINTR; >> } >> + ret = vma_dup_some(old_mm, mm); >> + if (ret) { >> + mmap_read_unlock(old_mm); >> + mutex_unlock(&tsk->signal->exec_update_mutex); >> + return ret; >> + } >> } >> >> task_lock(tsk); >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index dc7b87310c10..1c538ba77f33 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -295,11 +295,15 @@ int overcommit_kbytes_handler(struct ctl_table *, int, void *, size_t *, >> #define VM_HIGH_ARCH_BIT_2 34 /* bit only usable on 64-bit architectures */ >> #define VM_HIGH_ARCH_BIT_3 35 /* bit only usable on 64-bit architectures */ >> #define VM_HIGH_ARCH_BIT_4 36 /* bit only usable on 64-bit architectures */ >> +#define VM_HIGH_ARCH_BIT_5 37 /* bit only usable on 64-bit architectures */ >> #define VM_HIGH_ARCH_0 BIT(VM_HIGH_ARCH_BIT_0) >> #define VM_HIGH_ARCH_1 BIT(VM_HIGH_ARCH_BIT_1) >> #define VM_HIGH_ARCH_2 BIT(VM_HIGH_ARCH_BIT_2) >> #define VM_HIGH_ARCH_3 BIT(VM_HIGH_ARCH_BIT_3) >> #define VM_HIGH_ARCH_4 BIT(VM_HIGH_ARCH_BIT_4) >> +#define VM_EXEC_KEEP BIT(VM_HIGH_ARCH_BIT_5) /* preserve VMA across exec */ >> +#else >> +#define VM_EXEC_KEEP VM_NONE >> #endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */ >> >> #ifdef CONFIG_ARCH_HAS_PKEYS >> @@ -2534,6 +2538,7 @@ extern struct vm_area_struct *copy_vma(struct vm_area_struct **, >> unsigned long addr, unsigned long len, pgoff_t pgoff, >> bool *need_rmap_locks); >> extern void exit_mmap(struct mm_struct *); >> +extern int vma_dup(struct vm_area_struct *vma, struct mm_struct *mm); >> >> static inline int check_data_rlimit(unsigned long rlim, >> unsigned long new, >> diff --git a/kernel/fork.c b/kernel/fork.c >> index efc5493203ae..15ead613714f 100644 >> --- a/kernel/fork.c >> +++ b/kernel/fork.c >> @@ -564,7 +564,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, >> tmp->anon_vma = NULL; >> } else if (anon_vma_fork(tmp, mpnt)) >> goto fail_nomem_anon_vma_fork; >> - tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT); >> + tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT | VM_EXEC_KEEP); >> file = tmp->vm_file; >> if (file) { >> struct inode *inode = file_inode(file); >> diff --git a/mm/mmap.c b/mm/mmap.c >> index 59a4682ebf3f..be2ff53743c3 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -3279,6 +3279,53 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, >> return NULL; >> } >> >> +int vma_dup(struct vm_area_struct *old_vma, struct mm_struct *mm) >> +{ >> + unsigned long npages; >> + struct mm_struct *old_mm = old_vma->vm_mm; >> + struct vm_area_struct *vma; >> + int ret = -ENOMEM; >> + >> + if (WARN_ON(old_vma->vm_file || old_vma->vm_ops)) >> + return -EINVAL; >> + >> + vma = find_vma(mm, old_vma->vm_start); >> + if (vma && vma->vm_start < old_vma->vm_end) >> + return -EEXIST; >> + >> + npages = vma_pages(old_vma); >> + mm->total_vm += npages; > Why only total_vm? Where's exec_vm/stack_vm/data_vm? That was oversight.  Will be fixed in the next version. > >> + >> + vma = vm_area_dup(old_vma); >> + if (!vma) >> + goto fail_nomem; >> + >> + ret = vma_dup_policy(old_vma, vma); >> + if (ret) >> + goto fail_nomem_policy; >> + >> + vma->vm_mm = mm; >> + ret = anon_vma_fork(vma, old_vma); >> + if (ret) >> + goto fail_nomem_anon_vma_fork; > Looks like a duplication of code form dup_mmap(). > Any chance to get in one place? I looked at that, but dup_mmap() is dissimilar enough with the additional fork-specific code in dup_mmap() that I think readability would suffer. > >> + vma->vm_flags &= ~(VM_LOCKED|VM_UFFD_MISSING|VM_UFFD_WP|VM_EXEC_KEEP); >> + vma->vm_next = vma->vm_prev = NULL; > No need. vm_area_dup() takes care of it. Will fix. > >> + vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; > Semantics of VM_EXEC_KEEP vs userfaultfd() deserves a detailed explanation. > I feel these flags has to be mutually exclusive. Yes, will document this better. I think it's okay to mark userfaultfd-enabled memory for preservation as long as it is understood that memory would need to re-registered with userfaultfd() after exec and restore, if desired.  Unless there's a particular issue you see with this? Thanks, Anthony > >> + if (is_vm_hugetlb_page(vma)) >> + reset_vma_resv_huge_pages(vma); >> + __insert_vm_struct(mm, vma); >> + ret = copy_page_range(mm, old_mm, old_vma); >> + return ret; >> + >> +fail_nomem_anon_vma_fork: >> + mpol_put(vma_policy(vma)); >> +fail_nomem_policy: >> + vm_area_free(vma); >> +fail_nomem: >> + return -ENOMEM; >> +} >> + >> /* >> * Return true if the calling process may expand its vm space by the passed >> * number of pages >> -- >> 1.8.3.1 >> >> From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [RFC PATCH 3/5] mm: introduce VM_EXEC_KEEP References: <1595869887-23307-1-git-send-email-anthony.yznaga@oracle.com> <1595869887-23307-4-git-send-email-anthony.yznaga@oracle.com> <20200729135211.zodforvnv2xvdchm@box> From: Anthony Yznaga Message-ID: Date: Wed, 29 Jul 2020 16:20:32 -0700 MIME-Version: 1.0 In-Reply-To: <20200729135211.zodforvnv2xvdchm@box> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org To: "Kirill A. Shutemov" Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, mhocko@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, arnd@arndb.de, ebiederm@xmission.com, keescook@chromium.org, gerg@linux-m68k.org, ktkhai@virtuozzo.com, christian.brauner@ubuntu.com, peterz@infradead.org, esyr@redhat.com, jgg@ziepe.ca, christian@kellner.me, areber@redhat.com, cyphar@cyphar.com, steven.sistare@oracle.com List-ID: Message-ID: <20200729232032.dEXrEe9rPGUsxgndjJQd4E7mQEZD2b0Azq11Z4i2YDI@z> On 7/29/20 6:52 AM, Kirill A. Shutemov wrote: > On Mon, Jul 27, 2020 at 10:11:25AM -0700, Anthony Yznaga wrote: >> A vma with the VM_EXEC_KEEP flag is preserved across exec. For anonym= ous >> vmas only. For safety, overlap with fixed address VMAs created in the= new >> mm during exec (e.g. the stack and elf load segments) is not permitted= and >> will cause the exec to fail. >> (We are studying how to guarantee there are no conflicts. Comments wel= come.) >> >> Signed-off-by: Steve Sistare >> Signed-off-by: Anthony Yznaga >> --- >> arch/x86/Kconfig | 1 + >> fs/exec.c | 20 ++++++++++++++++++++ >> include/linux/mm.h | 5 +++++ >> kernel/fork.c | 2 +- >> mm/mmap.c | 47 +++++++++++++++++++++++++++++++++++++++++++++= ++ >> 5 files changed, 74 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >> index 883da0abf779..fc36eb2f45c0 100644 >> --- a/arch/x86/Kconfig >> +++ b/arch/x86/Kconfig >> @@ -30,6 +30,7 @@ config X86_64 >> select MODULES_USE_ELF_RELA >> select NEED_DMA_MAP_STATE >> select SWIOTLB >> + select ARCH_USES_HIGH_VMA_FLAGS >> =20 >> config FORCE_DYNAMIC_FTRACE >> def_bool y >> diff --git a/fs/exec.c b/fs/exec.c >> index 262112e5f9f8..1de09c4eef00 100644 >> --- a/fs/exec.c >> +++ b/fs/exec.c >> @@ -1069,6 +1069,20 @@ ssize_t read_code(struct file *file, unsigned l= ong addr, loff_t pos, size_t len) >> EXPORT_SYMBOL(read_code); >> #endif >> =20 >> +static int vma_dup_some(struct mm_struct *old_mm, struct mm_struct *n= ew_mm) >> +{ >> + struct vm_area_struct *vma; >> + int ret; >> + >> + for (vma =3D old_mm->mmap; vma; vma =3D vma->vm_next) >> + if (vma->vm_flags & VM_EXEC_KEEP) { >> + ret =3D vma_dup(vma, new_mm); >> + if (ret) >> + return ret; >> + } >> + return 0; >> +} >> + >> /* >> * Maps the mm_struct mm into the current task struct. >> * On success, this function returns with the mutex >> @@ -1104,6 +1118,12 @@ static int exec_mmap(struct mm_struct *mm) >> mutex_unlock(&tsk->signal->exec_update_mutex); >> return -EINTR; >> } >> + ret =3D vma_dup_some(old_mm, mm); >> + if (ret) { >> + mmap_read_unlock(old_mm); >> + mutex_unlock(&tsk->signal->exec_update_mutex); >> + return ret; >> + } >> } >> =20 >> task_lock(tsk); >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index dc7b87310c10..1c538ba77f33 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -295,11 +295,15 @@ int overcommit_kbytes_handler(struct ctl_table *= , int, void *, size_t *, >> #define VM_HIGH_ARCH_BIT_2 34 /* bit only usable on 64-bit architectu= res */ >> #define VM_HIGH_ARCH_BIT_3 35 /* bit only usable on 64-bit architectu= res */ >> #define VM_HIGH_ARCH_BIT_4 36 /* bit only usable on 64-bit architectu= res */ >> +#define VM_HIGH_ARCH_BIT_5 37 /* bit only usable on 64-bit architectu= res */ >> #define VM_HIGH_ARCH_0 BIT(VM_HIGH_ARCH_BIT_0) >> #define VM_HIGH_ARCH_1 BIT(VM_HIGH_ARCH_BIT_1) >> #define VM_HIGH_ARCH_2 BIT(VM_HIGH_ARCH_BIT_2) >> #define VM_HIGH_ARCH_3 BIT(VM_HIGH_ARCH_BIT_3) >> #define VM_HIGH_ARCH_4 BIT(VM_HIGH_ARCH_BIT_4) >> +#define VM_EXEC_KEEP BIT(VM_HIGH_ARCH_BIT_5) /* preserve VMA across e= xec */ >> +#else >> +#define VM_EXEC_KEEP VM_NONE >> #endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */ >> =20 >> #ifdef CONFIG_ARCH_HAS_PKEYS >> @@ -2534,6 +2538,7 @@ extern struct vm_area_struct *copy_vma(struct vm= _area_struct **, >> unsigned long addr, unsigned long len, pgoff_t pgoff, >> bool *need_rmap_locks); >> extern void exit_mmap(struct mm_struct *); >> +extern int vma_dup(struct vm_area_struct *vma, struct mm_struct *mm); >> =20 >> static inline int check_data_rlimit(unsigned long rlim, >> unsigned long new, >> diff --git a/kernel/fork.c b/kernel/fork.c >> index efc5493203ae..15ead613714f 100644 >> --- a/kernel/fork.c >> +++ b/kernel/fork.c >> @@ -564,7 +564,7 @@ static __latent_entropy int dup_mmap(struct mm_str= uct *mm, >> tmp->anon_vma =3D NULL; >> } else if (anon_vma_fork(tmp, mpnt)) >> goto fail_nomem_anon_vma_fork; >> - tmp->vm_flags &=3D ~(VM_LOCKED | VM_LOCKONFAULT); >> + tmp->vm_flags &=3D ~(VM_LOCKED | VM_LOCKONFAULT | VM_EXEC_KEEP); >> file =3D tmp->vm_file; >> if (file) { >> struct inode *inode =3D file_inode(file); >> diff --git a/mm/mmap.c b/mm/mmap.c >> index 59a4682ebf3f..be2ff53743c3 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -3279,6 +3279,53 @@ struct vm_area_struct *copy_vma(struct vm_area_= struct **vmap, >> return NULL; >> } >> =20 >> +int vma_dup(struct vm_area_struct *old_vma, struct mm_struct *mm) >> +{ >> + unsigned long npages; >> + struct mm_struct *old_mm =3D old_vma->vm_mm; >> + struct vm_area_struct *vma; >> + int ret =3D -ENOMEM; >> + >> + if (WARN_ON(old_vma->vm_file || old_vma->vm_ops)) >> + return -EINVAL; >> + >> + vma =3D find_vma(mm, old_vma->vm_start); >> + if (vma && vma->vm_start < old_vma->vm_end) >> + return -EEXIST; >> + >> + npages =3D vma_pages(old_vma); >> + mm->total_vm +=3D npages; > Why only total_vm? Where's exec_vm/stack_vm/data_vm? That was oversight.=C2=A0 Will be fixed in the next version. > >> + >> + vma =3D vm_area_dup(old_vma); >> + if (!vma) >> + goto fail_nomem; >> + >> + ret =3D vma_dup_policy(old_vma, vma); >> + if (ret) >> + goto fail_nomem_policy; >> + >> + vma->vm_mm =3D mm; >> + ret =3D anon_vma_fork(vma, old_vma); >> + if (ret) >> + goto fail_nomem_anon_vma_fork; > Looks like a duplication of code form dup_mmap(). > Any chance to get in one place? I looked at that, but dup_mmap() is dissimilar enough with the additional fork-specific code in dup_mmap() that I think readability would suffer. > >> + vma->vm_flags &=3D ~(VM_LOCKED|VM_UFFD_MISSING|VM_UFFD_WP|VM_EXEC_KE= EP); >> + vma->vm_next =3D vma->vm_prev =3D NULL; > No need. vm_area_dup() takes care of it. Will fix. > >> + vma->vm_userfaultfd_ctx =3D NULL_VM_UFFD_CTX; > Semantics of VM_EXEC_KEEP vs userfaultfd() deserves a detailed explanat= ion. > I feel these flags has to be mutually exclusive. Yes, will document this better. I think it's okay to mark userfaultfd-enabled memory for preservation as long as it is understood that memory would need to re-registered with userfaultfd() after exec and restore, if desired.=C2=A0 Unless there= 's a particular issue you see with this? Thanks, Anthony > >> + if (is_vm_hugetlb_page(vma)) >> + reset_vma_resv_huge_pages(vma); >> + __insert_vm_struct(mm, vma); >> + ret =3D copy_page_range(mm, old_mm, old_vma); >> + return ret; >> + >> +fail_nomem_anon_vma_fork: >> + mpol_put(vma_policy(vma)); >> +fail_nomem_policy: >> + vm_area_free(vma); >> +fail_nomem: >> + return -ENOMEM; >> +} >> + >> /* >> * Return true if the calling process may expand its vm space by the = passed >> * number of pages >> --=20 >> 1.8.3.1 >> >>