From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
vma_to_resize() is used in two locations to find and validate the vma
for the mremap location. One of the two locations already has the vma,
which is then re-found to validate the same vma.
This code can be simplified by moving the vma_lookup() from
vma_to_resize() to mremap_to() and changing the return type to an int
error.
Since the function now just validates the vma, the function is renamed
to mremap_vma_check() to better reflect what it is doing.
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
---
mm/mremap.c | 39 +++++++++++++++++++--------------------
1 file changed, 19 insertions(+), 20 deletions(-)
diff --git a/mm/mremap.c b/mm/mremap.c
index 5917feafe8cc..648c29f568af 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -826,17 +826,12 @@ static unsigned long move_vma(struct vm_area_struct *vma,
return new_addr;
}
-static struct vm_area_struct *vma_to_resize(unsigned long addr,
+static int mremap_vma_check(struct vm_area_struct *vma, unsigned long addr,
unsigned long old_len, unsigned long new_len, unsigned long flags)
{
struct mm_struct *mm = current->mm;
- struct vm_area_struct *vma;
unsigned long pgoff;
- vma = vma_lookup(mm, addr);
- if (!vma)
- return ERR_PTR(-EFAULT);
-
/*
* !old_len is a special case where an attempt is made to 'duplicate'
* a mapping. This makes no sense for private mappings as it will
@@ -847,37 +842,37 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
*/
if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current->comm, current->pid);
- return ERR_PTR(-EINVAL);
+ return -EINVAL;
}
if ((flags & MREMAP_DONTUNMAP) &&
(vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)))
- return ERR_PTR(-EINVAL);
+ return -EINVAL;
/* We can't remap across vm area boundaries */
if (old_len > vma->vm_end - addr)
- return ERR_PTR(-EFAULT);
+ return -EFAULT;
if (new_len == old_len)
- return vma;
+ return 0;
/* Need to be careful about a growing mapping */
pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
pgoff += vma->vm_pgoff;
if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
- return ERR_PTR(-EINVAL);
+ return -EINVAL;
if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
- return ERR_PTR(-EFAULT);
+ return -EFAULT;
if (!mlock_future_ok(mm, vma->vm_flags, new_len - old_len))
- return ERR_PTR(-EAGAIN);
+ return -EAGAIN;
if (!may_expand_vm(mm, vma->vm_flags,
(new_len - old_len) >> PAGE_SHIFT))
- return ERR_PTR(-ENOMEM);
+ return -ENOMEM;
- return vma;
+ return 0;
}
static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
@@ -936,7 +931,13 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
old_len = new_len;
}
- vma = vma_to_resize(addr, old_len, new_len, flags);
+ vma = vma_lookup(mm, addr);
+ if (!vma) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ mremap_vma_check(vma, addr, old_len, new_len, flags);
if (IS_ERR(vma)) {
ret = PTR_ERR(vma);
goto out;
@@ -1114,11 +1115,9 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
/*
* Ok, we need to grow..
*/
- vma = vma_to_resize(addr, old_len, new_len, flags);
- if (IS_ERR(vma)) {
- ret = PTR_ERR(vma);
+ ret = mremap_vma_check(vma, addr, old_len, new_len, flags);
+ if (ret)
goto out;
- }
/* old_len exactly to the end of the area..
*/
--
2.43.0On Wed, Oct 16, 2024 at 1:17 PM Liam R. Howlett <Liam.Howlett@oracle.com> wrote:
>
> From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
>
> vma_to_resize() is used in two locations to find and validate the vma
> for the mremap location. One of the two locations already has the vma,
> which is then re-found to validate the same vma.
>
> This code can be simplified by moving the vma_lookup() from
> vma_to_resize() to mremap_to() and changing the return type to an int
> error.
>
> Since the function now just validates the vma, the function is renamed
> to mremap_vma_check() to better reflect what it is doing.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
> ---
> mm/mremap.c | 39 +++++++++++++++++++--------------------
> 1 file changed, 19 insertions(+), 20 deletions(-)
>
> diff --git a/mm/mremap.c b/mm/mremap.c
> index 5917feafe8cc..648c29f568af 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -826,17 +826,12 @@ static unsigned long move_vma(struct vm_area_struct *vma,
> return new_addr;
> }
>
> -static struct vm_area_struct *vma_to_resize(unsigned long addr,
> +static int mremap_vma_check(struct vm_area_struct *vma, unsigned long addr,
The original function is vma_to_resize, and mremap_vma_check is
missing this context.
Maybe mremap_vma_check_resize is a better name ?
> unsigned long old_len, unsigned long new_len, unsigned long flags)
> {
> struct mm_struct *mm = current->mm;
> - struct vm_area_struct *vma;
> unsigned long pgoff;
>
> - vma = vma_lookup(mm, addr);
> - if (!vma)
> - return ERR_PTR(-EFAULT);
> -
> /*
> * !old_len is a special case where an attempt is made to 'duplicate'
> * a mapping. This makes no sense for private mappings as it will
> @@ -847,37 +842,37 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
> */
> if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
> pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current->comm, current->pid);
> - return ERR_PTR(-EINVAL);
> + return -EINVAL;
> }
>
> if ((flags & MREMAP_DONTUNMAP) &&
> (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)))
> - return ERR_PTR(-EINVAL);
> + return -EINVAL;
>
> /* We can't remap across vm area boundaries */
> if (old_len > vma->vm_end - addr)
> - return ERR_PTR(-EFAULT);
> + return -EFAULT;
>
> if (new_len == old_len)
> - return vma;
> + return 0;
>
> /* Need to be careful about a growing mapping */
> pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
> pgoff += vma->vm_pgoff;
> if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
> - return ERR_PTR(-EINVAL);
> + return -EINVAL;
>
> if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
> - return ERR_PTR(-EFAULT);
> + return -EFAULT;
>
> if (!mlock_future_ok(mm, vma->vm_flags, new_len - old_len))
> - return ERR_PTR(-EAGAIN);
> + return -EAGAIN;
>
> if (!may_expand_vm(mm, vma->vm_flags,
> (new_len - old_len) >> PAGE_SHIFT))
> - return ERR_PTR(-ENOMEM);
> + return -ENOMEM;
>
> - return vma;
> + return 0;
> }
>
> static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
> @@ -936,7 +931,13 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
> old_len = new_len;
> }
>
> - vma = vma_to_resize(addr, old_len, new_len, flags);
> + vma = vma_lookup(mm, addr);
> + if (!vma) {
> + ret = -EFAULT;
> + goto out;
> + }
> +
> + mremap_vma_check(vma, addr, old_len, new_len, flags);
> if (IS_ERR(vma)) {
> ret = PTR_ERR(vma);
> goto out;
> @@ -1114,11 +1115,9 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
> /*
> * Ok, we need to grow..
> */
> - vma = vma_to_resize(addr, old_len, new_len, flags);
> - if (IS_ERR(vma)) {
> - ret = PTR_ERR(vma);
> + ret = mremap_vma_check(vma, addr, old_len, new_len, flags);
> + if (ret)
> goto out;
> - }
>
> /* old_len exactly to the end of the area..
> */
> --
> 2.43.0
>
* Jeff Xu <jeffxu@chromium.org> [241017 13:55]: > On Wed, Oct 16, 2024 at 1:17 PM Liam R. Howlett <Liam.Howlett@oracle.com> wrote: > > > > From: "Liam R. Howlett" <Liam.Howlett@Oracle.com> > > > > vma_to_resize() is used in two locations to find and validate the vma > > for the mremap location. One of the two locations already has the vma, > > which is then re-found to validate the same vma. > > > > This code can be simplified by moving the vma_lookup() from > > vma_to_resize() to mremap_to() and changing the return type to an int > > error. > > > > Since the function now just validates the vma, the function is renamed > > to mremap_vma_check() to better reflect what it is doing. > > > > Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com> > > --- > > mm/mremap.c | 39 +++++++++++++++++++-------------------- > > 1 file changed, 19 insertions(+), 20 deletions(-) > > > > diff --git a/mm/mremap.c b/mm/mremap.c > > index 5917feafe8cc..648c29f568af 100644 > > --- a/mm/mremap.c > > +++ b/mm/mremap.c > > @@ -826,17 +826,12 @@ static unsigned long move_vma(struct vm_area_struct *vma, > > return new_addr; > > } > > > > -static struct vm_area_struct *vma_to_resize(unsigned long addr, > > +static int mremap_vma_check(struct vm_area_struct *vma, unsigned long addr, > The original function is vma_to_resize, and mremap_vma_check is > missing this context. > Maybe mremap_vma_check_resize is a better name ? Good point. That suggestion is long though. Perhaps vma_check_resize(), since this is a static function in the mremap.c file, it is fine to drop mremap from the name. ... Thanks, Liam
On Thu, Oct 17, 2024 at 11:07 AM Liam R. Howlett <Liam.Howlett@oracle.com> wrote: > > * Jeff Xu <jeffxu@chromium.org> [241017 13:55]: > > On Wed, Oct 16, 2024 at 1:17 PM Liam R. Howlett <Liam.Howlett@oracle.com> wrote: > > > > > > From: "Liam R. Howlett" <Liam.Howlett@Oracle.com> > > > > > > vma_to_resize() is used in two locations to find and validate the vma > > > for the mremap location. One of the two locations already has the vma, > > > which is then re-found to validate the same vma. > > > > > > This code can be simplified by moving the vma_lookup() from > > > vma_to_resize() to mremap_to() and changing the return type to an int > > > error. > > > > > > Since the function now just validates the vma, the function is renamed > > > to mremap_vma_check() to better reflect what it is doing. > > > > > > Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com> > > > --- > > > mm/mremap.c | 39 +++++++++++++++++++-------------------- > > > 1 file changed, 19 insertions(+), 20 deletions(-) > > > > > > diff --git a/mm/mremap.c b/mm/mremap.c > > > index 5917feafe8cc..648c29f568af 100644 > > > --- a/mm/mremap.c > > > +++ b/mm/mremap.c > > > @@ -826,17 +826,12 @@ static unsigned long move_vma(struct vm_area_struct *vma, > > > return new_addr; > > > } > > > > > > -static struct vm_area_struct *vma_to_resize(unsigned long addr, > > > +static int mremap_vma_check(struct vm_area_struct *vma, unsigned long addr, > > The original function is vma_to_resize, and mremap_vma_check is > > missing this context. > > Maybe mremap_vma_check_resize is a better name ? > > Good point. That suggestion is long though. Perhaps > vma_check_resize(), since this is a static function in the mremap.c > file, it is fine to drop mremap from the name. > I'm ok with that. > ... > > Thanks, > Liam
On Thu, 17 Oct 2024 11:15:20 -0700 Jeff Xu <jeffxu@chromium.org> wrote: > > > > -static struct vm_area_struct *vma_to_resize(unsigned long addr, > > > > +static int mremap_vma_check(struct vm_area_struct *vma, unsigned long addr, > > > The original function is vma_to_resize, and mremap_vma_check is > > > missing this context. > > > Maybe mremap_vma_check_resize is a better name ? > > > > Good point. That suggestion is long though. Perhaps > > vma_check_resize(), since this is a static function in the mremap.c > > file, it is fine to drop mremap from the name. > > > I'm ok with that. Any function with "check" in the name makes my teeth ache. "check" what? And the name doesn't carry any connotation of the return value's meaning. eg, "check_the_cheese()" versus "cheese_is_fresh()". The latter name tells you what is being checked and it tells you what a "true" return value means. Also, the dang function isn't documented. Also, why is mremap_to() calling mremap_vma_check() without testing its return value? mremap_vma_check() doesn't actually alter anything, does it? If it does then it's misnamed.
* Andrew Morton <akpm@linux-foundation.org> [241017 17:08]: > On Thu, 17 Oct 2024 11:15:20 -0700 Jeff Xu <jeffxu@chromium.org> wrote: > > > > > > -static struct vm_area_struct *vma_to_resize(unsigned long addr, > > > > > +static int mremap_vma_check(struct vm_area_struct *vma, unsigned long addr, > > > > The original function is vma_to_resize, and mremap_vma_check is > > > > missing this context. > > > > Maybe mremap_vma_check_resize is a better name ? > > > > > > Good point. That suggestion is long though. Perhaps > > > vma_check_resize(), since this is a static function in the mremap.c > > > file, it is fine to drop mremap from the name. > > > > > I'm ok with that. > > Any function with "check" in the name makes my teeth ache. "check" > what? And the name doesn't carry any connotation of the return value's > meaning. > > eg, "check_the_cheese()" versus "cheese_is_fresh()". The latter name > tells you what is being checked and it tells you what a "true" return > value means. Fair enough, how about resize_is_valid()? > > Also, the dang function isn't documented. I'll add that, thanks. > > Also, why is mremap_to() calling mremap_vma_check() without testing its > return value? mremap_vma_check() doesn't actually alter anything, does > it? If it does then it's misnamed. That's an issue, I'll fix it. Thanks, Liam
On Thu, 17 Oct 2024 19:53:10 -0400 "Liam R. Howlett" <Liam.Howlett@oracle.com> wrote: > > eg, "check_the_cheese()" versus "cheese_is_fresh()". The latter name > > tells you what is being checked and it tells you what a "true" return > > value means. > > Fair enough, how about resize_is_valid()? Sounds great. Although I do prefer cheese_is_fresh().
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