Commit 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is
invalid") made mmap() return EINVAL if PROT_WRITE was set wihtout
PROT_READ with the justification that a write-only PTE is considered a
reserved PTE permission bit pattern in the privileged spec. This check
is unnecessary since we let VM_WRITE imply VM_READ on RISC-V, and it is
inconsistent with other architectures that don't support write-only PTEs,
creating a potential software portability issue. Just remove the check
altogether and let PROT_WRITE imply PROT_READ as is the case on other
architectures.
Note that this also allows PROT_WRITE|PROT_EXEC mappings which were
disallowed prior to the aforementioned commit; PROT_READ is implied in
such mappings as well.
Fixes: 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is invalid")
Reviewed-by: Atish Patra <[email protected]>
Signed-off-by: Andrew Bresticker <[email protected]>
---
v1 -> v2: Update access_error() to account for write-implies-read
v2 -> v3: Separate into two commits
---
arch/riscv/kernel/sys_riscv.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c
index 571556bb9261..5d3f2fbeb33c 100644
--- a/arch/riscv/kernel/sys_riscv.c
+++ b/arch/riscv/kernel/sys_riscv.c
@@ -18,9 +18,6 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len,
if (unlikely(offset & (~PAGE_MASK >> page_shift_offset)))
return -EINVAL;
- if (unlikely((prot & PROT_WRITE) && !(prot & PROT_READ)))
- return -EINVAL;
-
return ksys_mmap_pgoff(addr, len, prot, flags, fd,
offset >> (PAGE_SHIFT - page_shift_offset));
}
--
2.25.1
On 09/09/2022 22:27, Andrew Bresticker wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>
> Commit 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is
> invalid") made mmap() return EINVAL if PROT_WRITE was set wihtout
> PROT_READ with the justification that a write-only PTE is considered a
> reserved PTE permission bit pattern in the privileged spec. This check
> is unnecessary since we let VM_WRITE imply VM_READ on RISC-V, and it is
> inconsistent with other architectures that don't support write-only PTEs,
> creating a potential software portability issue. Just remove the check
> altogether and let PROT_WRITE imply PROT_READ as is the case on other
> architectures.
>
> Note that this also allows PROT_WRITE|PROT_EXEC mappings which were
> disallowed prior to the aforementioned commit; PROT_READ is implied in
> such mappings as well.
>
> Fixes: 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is invalid")
For the naive members of the audience such as myself, this patch
came after a non-fixes patch in the series. What is the dependence
of this patch on the other one (if any)?
Thanks,
Conor.
> Reviewed-by: Atish Patra <[email protected]>
> Signed-off-by: Andrew Bresticker <[email protected]>
> ---
> v1 -> v2: Update access_error() to account for write-implies-read
> v2 -> v3: Separate into two commits
> ---
> arch/riscv/kernel/sys_riscv.c | 3 ---
> 1 file changed, 3 deletions(-)
>
> diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c
> index 571556bb9261..5d3f2fbeb33c 100644
> --- a/arch/riscv/kernel/sys_riscv.c
> +++ b/arch/riscv/kernel/sys_riscv.c
> @@ -18,9 +18,6 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len,
> if (unlikely(offset & (~PAGE_MASK >> page_shift_offset)))
> return -EINVAL;
>
> - if (unlikely((prot & PROT_WRITE) && !(prot & PROT_READ)))
> - return -EINVAL;
> -
> return ksys_mmap_pgoff(addr, len, prot, flags, fd,
> offset >> (PAGE_SHIFT - page_shift_offset));
> }
> --
> 2.25.1
>
>
> _______________________________________________
> linux-riscv mailing list
> [email protected]
> http://lists.infradead.org/mailman/listinfo/linux-riscv
On Thu, Sep 15, 2022 at 12:56 PM <[email protected]> wrote:
>
> On 09/09/2022 22:27, Andrew Bresticker wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> >
> > Commit 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is
> > invalid") made mmap() return EINVAL if PROT_WRITE was set wihtout
> > PROT_READ with the justification that a write-only PTE is considered a
> > reserved PTE permission bit pattern in the privileged spec. This check
> > is unnecessary since we let VM_WRITE imply VM_READ on RISC-V, and it is
> > inconsistent with other architectures that don't support write-only PTEs,
> > creating a potential software portability issue. Just remove the check
> > altogether and let PROT_WRITE imply PROT_READ as is the case on other
> > architectures.
> >
> > Note that this also allows PROT_WRITE|PROT_EXEC mappings which were
> > disallowed prior to the aforementioned commit; PROT_READ is implied in
> > such mappings as well.
> >
> > Fixes: 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is invalid")
>
> For the naive members of the audience such as myself, this patch
> came after a non-fixes patch in the series. What is the dependence
> of this patch on the other one (if any)?
This patch is dependent on the first. Happy to re-spin with a "Fixes"
tag on the first patch (or maybe Palmer can add when applying).
-Andrew
> Thanks,
> Conor.
>
> > Reviewed-by: Atish Patra <[email protected]>
> > Signed-off-by: Andrew Bresticker <[email protected]>
> > ---
> > v1 -> v2: Update access_error() to account for write-implies-read
> > v2 -> v3: Separate into two commits
> > ---
> > arch/riscv/kernel/sys_riscv.c | 3 ---
> > 1 file changed, 3 deletions(-)
> >
> > diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c
> > index 571556bb9261..5d3f2fbeb33c 100644
> > --- a/arch/riscv/kernel/sys_riscv.c
> > +++ b/arch/riscv/kernel/sys_riscv.c
> > @@ -18,9 +18,6 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len,
> > if (unlikely(offset & (~PAGE_MASK >> page_shift_offset)))
> > return -EINVAL;
> >
> > - if (unlikely((prot & PROT_WRITE) && !(prot & PROT_READ)))
> > - return -EINVAL;
> > -
> > return ksys_mmap_pgoff(addr, len, prot, flags, fd,
> > offset >> (PAGE_SHIFT - page_shift_offset));
> > }
> > --
> > 2.25.1
> >
> >
> > _______________________________________________
> > linux-riscv mailing list
> > [email protected]
> > http://lists.infradead.org/mailman/listinfo/linux-riscv
>
On 9/16/22 01:40, [email protected] wrote:
> On 15/09/2022 18:27, Andrew Bresticker wrote:
>> On Thu, Sep 15, 2022 at 12:56 PM <[email protected]> wrote:
>>> On 09/09/2022 22:27, Andrew Bresticker wrote:
>>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>>
>>>> Commit 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is
>>>> invalid") made mmap() return EINVAL if PROT_WRITE was set wihtout
>>>> PROT_READ with the justification that a write-only PTE is considered a
>>>> reserved PTE permission bit pattern in the privileged spec. This check
>>>> is unnecessary since we let VM_WRITE imply VM_READ on RISC-V, and it is
>>>> inconsistent with other architectures that don't support write-only PTEs,
>>>> creating a potential software portability issue. Just remove the check
>>>> altogether and let PROT_WRITE imply PROT_READ as is the case on other
>>>> architectures.
>>>>
>>>> Note that this also allows PROT_WRITE|PROT_EXEC mappings which were
>>>> disallowed prior to the aforementioned commit; PROT_READ is implied in
>>>> such mappings as well.
>>>>
>>>> Fixes: 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is invalid")
>>> For the naive members of the audience such as myself, this patch
>>> came after a non-fixes patch in the series. What is the dependence
>>> of this patch on the other one (if any)?
>> This patch is dependent on the first. Happy to re-spin with a "Fixes"
>> tag on the first patch (or maybe Palmer can add when applying).
> If it is a fix, then it should have a fixes tag. If it's cosmetic reorg
> to make the fix easier then no & it should be moved after the fix. If
> it is neither then you should prob mention it in the cover or under the
> --- /shrug
Basically what happens fixes-wise is that patch 1 fixes the original
problem in a different way, and patch 2 undoes the previous patch (with
small additional fixes). IMO this needs a cover to explain what's going
on to those who missed the v1 and v2 discussion thread.
v1 here: https://lore.kernel.org/all/[email protected]
Thanks,
dram
> Thanks,
> Conor.
>
>>>> Reviewed-by: Atish Patra <[email protected]>
>>>> Signed-off-by: Andrew Bresticker <[email protected]>
>>>> ---
>>>> v1 -> v2: Update access_error() to account for write-implies-read
>>>> v2 -> v3: Separate into two commits
>>>> ---
>>>> arch/riscv/kernel/sys_riscv.c | 3 ---
>>>> 1 file changed, 3 deletions(-)
>>>>
>>>> diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c
>>>> index 571556bb9261..5d3f2fbeb33c 100644
>>>> --- a/arch/riscv/kernel/sys_riscv.c
>>>> +++ b/arch/riscv/kernel/sys_riscv.c
>>>> @@ -18,9 +18,6 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len,
>>>> if (unlikely(offset & (~PAGE_MASK >> page_shift_offset)))
>>>> return -EINVAL;
>>>>
>>>> - if (unlikely((prot & PROT_WRITE) && !(prot & PROT_READ)))
>>>> - return -EINVAL;
>>>> -
>>>> return ksys_mmap_pgoff(addr, len, prot, flags, fd,
>>>> offset >> (PAGE_SHIFT - page_shift_offset));
>>>> }
>>>> --
>>>> 2.25.1
>>>>
>>>>
>>>> _______________________________________________
>>>> linux-riscv mailing list
>>>> [email protected]
>>>> http://lists.infradead.org/mailman/listinfo/linux-riscv
On 15/09/2022 18:27, Andrew Bresticker wrote:
> On Thu, Sep 15, 2022 at 12:56 PM <[email protected]> wrote:
>>
>> On 09/09/2022 22:27, Andrew Bresticker wrote:
>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>
>>> Commit 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is
>>> invalid") made mmap() return EINVAL if PROT_WRITE was set wihtout
>>> PROT_READ with the justification that a write-only PTE is considered a
>>> reserved PTE permission bit pattern in the privileged spec. This check
>>> is unnecessary since we let VM_WRITE imply VM_READ on RISC-V, and it is
>>> inconsistent with other architectures that don't support write-only PTEs,
>>> creating a potential software portability issue. Just remove the check
>>> altogether and let PROT_WRITE imply PROT_READ as is the case on other
>>> architectures.
>>>
>>> Note that this also allows PROT_WRITE|PROT_EXEC mappings which were
>>> disallowed prior to the aforementioned commit; PROT_READ is implied in
>>> such mappings as well.
>>>
>>> Fixes: 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is invalid")
>>
>> For the naive members of the audience such as myself, this patch
>> came after a non-fixes patch in the series. What is the dependence
>> of this patch on the other one (if any)?
>
> This patch is dependent on the first. Happy to re-spin with a "Fixes"
> tag on the first patch (or maybe Palmer can add when applying).
If it is a fix, then it should have a fixes tag. If it's cosmetic reorg
to make the fix easier then no & it should be moved after the fix. If
it is neither then you should prob mention it in the cover or under the
--- /shrug
Thanks,
Conor.
>>> Reviewed-by: Atish Patra <[email protected]>
>>> Signed-off-by: Andrew Bresticker <[email protected]>
>>> ---
>>> v1 -> v2: Update access_error() to account for write-implies-read
>>> v2 -> v3: Separate into two commits
>>> ---
>>> arch/riscv/kernel/sys_riscv.c | 3 ---
>>> 1 file changed, 3 deletions(-)
>>>
>>> diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c
>>> index 571556bb9261..5d3f2fbeb33c 100644
>>> --- a/arch/riscv/kernel/sys_riscv.c
>>> +++ b/arch/riscv/kernel/sys_riscv.c
>>> @@ -18,9 +18,6 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len,
>>> if (unlikely(offset & (~PAGE_MASK >> page_shift_offset)))
>>> return -EINVAL;
>>>
>>> - if (unlikely((prot & PROT_WRITE) && !(prot & PROT_READ)))
>>> - return -EINVAL;
>>> -
>>> return ksys_mmap_pgoff(addr, len, prot, flags, fd,
>>> offset >> (PAGE_SHIFT - page_shift_offset));
>>> }
>>> --
>>> 2.25.1
>>>
>>>
>>> _______________________________________________
>>> linux-riscv mailing list
>>> [email protected]
>>> http://lists.infradead.org/mailman/listinfo/linux-riscv
>>