Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Petr Tesarik <> | Subject | [PATCH 2/2] um: oops on accessing an non-present page in the vmalloc area | Date | Fri, 15 Dec 2023 13:14:31 +0100 |
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From: Petr Tesarik <petr.tesarik1@huawei-partners.com>
If a segmentation fault is caused by an address in the vmalloc area, check that the target page is present.
Currently, if the kernel hits a guard page the vmalloc area, UML assumes that the fault is caused merely by a stale mapping and will be fixed by flush_tlb_kernel_vm(). Of course, this will not create any mapping for a guard page, so the faulting instruction will cause exactly the same fault when it is executed again, effectively creating a beautiful (but useless) infinite loop.
Signed-off-by: Petr Tesarik <petr.tesarik1@huawei-partners.com> --- arch/um/kernel/trap.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c index 1124a382fd14..ca9b5fd83c52 100644 --- a/arch/um/kernel/trap.c +++ b/arch/um/kernel/trap.c @@ -214,11 +214,15 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, int err; int is_write = FAULT_WRITE(fi); unsigned long address = FAULT_ADDRESS(fi); + pte_t *pte; if (!is_user && regs) current->thread.segv_regs = container_of(regs, struct pt_regs, regs); if (!is_user && (address >= start_vm) && (address < end_vm)) { + pte = virt_to_pte(&init_mm, address); + if (!pte_present(*pte)) + page_fault_oops(regs, address, ip); flush_tlb_kernel_vm(); goto out; } -- 2.34.1
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