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Date: Fri, 11 Jun 2021 19:02:26 +0100
From: Dmitry Safonov <dima@...sta.com>
To: linux-kernel@...r.kernel.org
Cc: Dmitry Safonov <0x7f454c46@...il.com>,
Dmitry Safonov <dima@...sta.com>,
Alexander Viro <viro@...iv.linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>,
Andy Lutomirski <luto@...nel.org>,
Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
Catalin Marinas <catalin.marinas@....com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Guo Ren <guoren@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
Ingo Molnar <mingo@...hat.com>,
Oleg Nesterov <oleg@...hat.com>,
Russell King <linux@...linux.org.uk>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
Thomas Gleixner <tglx@...utronix.de>,
Vincenzo Frascino <vincenzo.frascino@....com>,
Will Deacon <will@...nel.org>, x86@...nel.org
Subject: [PATCH v3 07/23] vdso: Set mm->context.vdso only on success of _install_special_mapping()
Old pattern was:
1. set mm->context.vdso = addr;
2. try install_special_mapping()
3. on failure set mm->context.vdso = 0
The reason behind the old pattern was to make arch_vma_name() work
in perf_event_mmap_event(). These days using _install_special_mapping()
instead of install_special_mapping() makes old pattern obsolete:
: if (vma->vm_ops && vma->vm_ops->name) {
: name = (char *) vma->vm_ops->name(vma);
: if (name)
: goto cpy_name;
Setting mm->context.vdso = 0 also makes little sense: mm_alloc()
zero-fills new mm_struct. And for double-safety if
arch_setup_additional_pages() fails, bprm_execve() makes sure that the
half-initialized process doesn't make it way to userspace by
: force_sigsegv(SIGSEGV);
Let's cleanup code: set mm->context.vdso only on success, assuming that
any new mm_struct is clean.
Some platforms do_munmap() vvar if vdso mapping failed, but it's really
necessary only on x86 where vdso/vvar pair can be mapped by userspace
(see prctl_map_vdso()). On other platforms vdso/vvar is only pre-mapped
by ELF loader, which as described above will make sure to not let any
half-baked process out. I've left do_unmap() on !x86 in case prctl()
will be supported.
Signed-off-by: Dmitry Safonov <dima@...sta.com>
---
arch/arm/kernel/vdso.c | 2 --
arch/arm64/kernel/vdso.c | 16 +++++-----------
arch/nds32/kernel/vdso.c | 5 +----
arch/powerpc/kernel/vdso.c | 9 ++-------
arch/sparc/vdso/vma.c | 7 ++-----
5 files changed, 10 insertions(+), 29 deletions(-)
diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c
index 3408269d19c7..015eff0a6e93 100644
--- a/arch/arm/kernel/vdso.c
+++ b/arch/arm/kernel/vdso.c
@@ -238,8 +238,6 @@ void arm_install_vdso(struct mm_struct *mm, unsigned long addr)
struct vm_area_struct *vma;
unsigned long len;
- mm->context.vdso = 0;
-
if (vdso_text_pagelist == NULL)
return;
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index a8bf72320ad0..1bc8adefa293 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -227,34 +227,28 @@ static int __setup_additional_pages(enum vdso_abi abi,
vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
- if (IS_ERR_VALUE(vdso_base)) {
- ret = ERR_PTR(vdso_base);
- goto up_fail;
- }
+ if (IS_ERR_VALUE(vdso_base))
+ return vdso_base;
ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
VM_READ|VM_MAYREAD|VM_PFNMAP,
vdso_info[abi].dm);
if (IS_ERR(ret))
- goto up_fail;
+ return PTR_ERR(ret);
if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
gp_flags = VM_ARM64_BTI;
vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
- mm->context.vdso = (void *)vdso_base;
ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
VM_READ|VM_EXEC|gp_flags|
VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
vdso_info[abi].cm);
if (IS_ERR(ret))
- goto up_fail;
+ return PTR_ERR(ret);
+ mm->context.vdso = (void *)vdso_base;
return 0;
-
-up_fail:
- mm->context.vdso = NULL;
- return PTR_ERR(ret);
}
#ifdef CONFIG_COMPAT
diff --git a/arch/nds32/kernel/vdso.c b/arch/nds32/kernel/vdso.c
index e16009a07971..2d1d51a0fc64 100644
--- a/arch/nds32/kernel/vdso.c
+++ b/arch/nds32/kernel/vdso.c
@@ -175,7 +175,6 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
/*Map vdso to user space */
vdso_base += PAGE_SIZE;
- mm->context.vdso = (void *)vdso_base;
vma = _install_special_mapping(mm, vdso_base, vdso_text_len,
VM_READ | VM_EXEC |
VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
@@ -185,11 +184,9 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
goto up_fail;
}
- mmap_write_unlock(mm);
- return 0;
+ mm->context.vdso = (void *)vdso_base;
up_fail:
- mm->context.vdso = NULL;
mmap_write_unlock(mm);
return ret;
}
diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index 717f2c9a7573..76e898b56002 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -229,13 +229,6 @@ static int __arch_setup_additional_pages(struct linux_binprm *bprm, int uses_int
/* Add required alignment. */
vdso_base = ALIGN(vdso_base, VDSO_ALIGNMENT);
- /*
- * Put vDSO base into mm struct. We need to do this before calling
- * install_special_mapping or the perf counter mmap tracking code
- * will fail to recognise it as a vDSO.
- */
- mm->context.vdso = (void __user *)vdso_base + vvar_size;
-
vma = _install_special_mapping(mm, vdso_base, vvar_size,
VM_READ | VM_MAYREAD | VM_IO |
VM_DONTDUMP | VM_PFNMAP, &vvar_spec);
@@ -257,6 +250,8 @@ static int __arch_setup_additional_pages(struct linux_binprm *bprm, int uses_int
VM_MAYWRITE | VM_MAYEXEC, vdso_spec);
if (IS_ERR(vma))
do_munmap(mm, vdso_base, vvar_size, NULL);
+ else
+ mm->context.vdso = (void __user *)vdso_base + vvar_size;
return PTR_ERR_OR_ZERO(vma);
}
diff --git a/arch/sparc/vdso/vma.c b/arch/sparc/vdso/vma.c
index cc19e09b0fa1..d8a344f6c914 100644
--- a/arch/sparc/vdso/vma.c
+++ b/arch/sparc/vdso/vma.c
@@ -390,7 +390,6 @@ static int map_vdso(const struct vdso_image *image,
}
text_start = addr - image->sym_vvar_start;
- current->mm->context.vdso = (void __user *)text_start;
/*
* MAYWRITE to allow gdb to COW and set breakpoints
@@ -412,16 +411,14 @@ static int map_vdso(const struct vdso_image *image,
-image->sym_vvar_start,
VM_READ|VM_MAYREAD,
&vvar_mapping);
-
if (IS_ERR(vma)) {
ret = PTR_ERR(vma);
do_munmap(mm, text_start, image->size, NULL);
+ } else {
+ current->mm->context.vdso = (void __user *)text_start;
}
up_fail:
- if (ret)
- current->mm->context.vdso = NULL;
-
mmap_write_unlock(mm);
return ret;
}
--
2.31.1
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