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riscv/mm: Prevent kernel module to access user memory without uaccess routines

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We found this issue in an legacy out-of-tree kernel module
which didn't properly access user space pointer by get/put_user().
Such an illegal access loops in the page fault handler.
To resolve this, let it die here.

Signed-off-by: Eric Lin <tesheng@andestech.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
This commit is contained in:
Eric Lin 2020-12-04 13:42:59 +08:00 committed by Palmer Dabbelt
parent 21733cb518
commit 21855cac82
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1 changed files with 5 additions and 0 deletions
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5
arch/riscv/mm/fault.c
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@ -243,6 +243,11 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
if (user_mode(regs))
flags |= FAULT_FLAG_USER;
if (!user_mode(regs) && addr < TASK_SIZE &&
unlikely(!(regs->status & SR_SUM)))
die_kernel_fault("access to user memory without uaccess routines",
addr, regs);
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
if (cause == EXC_STORE_PAGE_FAULT)