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authorYash Shah <yash.shah@sifive.com>2020-06-16 19:33:06 +0530
committerPalmer Dabbelt <palmerdabbelt@google.com>2020-06-18 17:28:53 -0700
commite0d17c842c0f824fd4df9f4688709fc6907201e1 (patch)
treee53115d8f412b9e77e9519de3f5a3d3050c00501
parent6c58f25e6938c073198af8b1e1832f83f8f0df33 (diff)
downloadlinux-sh-e0d17c842c0f824fd4df9f4688709fc6907201e1.tar.gz
RISC-V: Don't allow write+exec only page mapping request in mmap
As per the table 4.4 of version "20190608-Priv-MSU-Ratified" of the RISC-V instruction set manual[0], the PTE permission bit combination of "write+exec only" is reserved for future use. Hence, don't allow such mapping request in mmap call. An issue is been reported by David Abdurachmanov, that while running stress-ng with "sysbadaddr" argument, RCU stalls are observed on RISC-V specific kernel. This issue arises when the stress-sysbadaddr request for pages with "write+exec only" permission bits and then passes the address obtain from this mmap call to various system call. For the riscv kernel, the mmap call should fail for this particular combination of permission bits since it's not valid. [0]: http://dabbelt.com/~palmer/keep/riscv-isa-manual/riscv-privileged-20190608-1.pdf Signed-off-by: Yash Shah <yash.shah@sifive.com> Reported-by: David Abdurachmanov <david.abdurachmanov@gmail.com> [Palmer: Refer to the latest ISA specification at the only link I could find, and update the terminology.] Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
-rw-r--r--arch/riscv/kernel/sys_riscv.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c
index f3619f59d85c..12f8a7fce78b 100644
--- a/arch/riscv/kernel/sys_riscv.c
+++ b/arch/riscv/kernel/sys_riscv.c
@@ -8,6 +8,7 @@
#include <linux/syscalls.h>
#include <asm/unistd.h>
#include <asm/cacheflush.h>
+#include <asm-generic/mman-common.h>
static long riscv_sys_mmap(unsigned long addr, unsigned long len,
unsigned long prot, unsigned long flags,
@@ -16,6 +17,11 @@ 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;
+
return ksys_mmap_pgoff(addr, len, prot, flags, fd,
offset >> (PAGE_SHIFT - page_shift_offset));
}