Messages in this thread | | | From | <> | Subject | Re: [PATCH v2] riscv: don't allow write but not read page mapping request in mmap | Date | Mon, 13 Jun 2022 06:25:22 +0000 |
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On 13/06/2022 06:20, Celeste Liu wrote: > [You don't often get email from coelacanthus@outlook.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ] > > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe > > When xctan tries to run one of libaio's tests > (https://pagure.io/libaio/blob/1b18bfafc6a2f7b9fa2c6be77a95afed8b7be448/f/harness/cases/5.t), > it encounters a strange behavior: for the same PROT_WRITE only mapping, > there was a discrepancy in whether it could be read before and after writing > (readable before writing, unreadable after writing). After some investigation, > I found that mmap allows write only mapping, an undefined behavior, on RISC-V. > > As mentioned in Table 4.5 in RISC-V spec Volume 2 Section 4.3 version > "20211203 Privileged Architecture v1.12, Ratified"[1], the PTE permission > bit combination of "write+!read" is "Reserved for future use.". Hence, don't > allow such mapping request in mmap call. In the current code[2], write+exec > only is marked as invalid, but write only is not marked as invalid. > > This patch refines that judgment. > > [1]: https://github.com/riscv/riscv-isa-manual/releases/download/Priv-v1.12/riscv-privileged-20211203.pdf > [2]: modified in commit e0d17c842c0f824fd4df9f4688709fc6907201e1 > (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e0d17c842c0f824fd4df9f4688709fc6907201e1) > > Reported-by: xctan <xc-tan@outlook.com> > Co-developed-by: dram <dramforever@live.com> > Signed-off-by: dram <dramforever@live.com>
Those don't look like "real" names? https://www.kernel.org/doc/html/latest/process/submitting-patches.html#sign-your-work-the-developer-s-certificate-of-origin
> Co-developed-by: Ruizhe Pan <c141028@gmail.com> > Signed-off-by: Ruizhe Pan <c141028@gmail.com> > Signed-off-by: Celeste Liu <coelacanthus@outlook.com> > Cc: linux-riscv@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Cc: Guo Ren <guoren@kernel.org> > Cc: Yash Shah <yash.shah@sifive.com> > --- > v2: This version adds a link to the referenced spec, and reference of the > previous related modification. > > arch/riscv/kernel/sys_riscv.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c > index 9c0194f176fc..571556bb9261 100644 > --- a/arch/riscv/kernel/sys_riscv.c > +++ b/arch/riscv/kernel/sys_riscv.c > @@ -18,9 +18,8 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len, > if (unlikely(offset & (~PAGE_MASK >> page_shift_offset))) > return -EINVAL; > > - if ((prot & PROT_WRITE) && (prot & PROT_EXEC)) > - if (unlikely(!(prot & PROT_READ))) > - 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)); > -- > 2.36.1 > > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv
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