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um: allocate a guard page to helper threads

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We've been running into stack overflows in helper threads
corrupting memory (e.g. because somebody put printf() or
os_info() there), so to avoid those causing hard-to-debug
issues later on, allocate a guard page for helper thread
stacks and mark it read-only.

Unfortunately, the crash dump at that point is useless as
the stack tracer will try to backtrace the *kernel* thread,
not the helper thread, but at least we don't survive to a
random issue caused by corruption.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Johannes Berg
2020-12-05 21:50:18 +01:00
committed by Richard Weinberger
parent 963285b0b4
commit ef4459a6da
4 changed files with 11 additions and 8 deletions
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2
arch/um/include/shared/kern_util.h
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@@ -19,7 +19,7 @@ extern int kmalloc_ok;
#define UML_ROUND_UP(addr) \
((((unsigned long) addr) + PAGE_SIZE - 1) & PAGE_MASK)
extern unsigned long alloc_stack(int order, int atomic);
extern unsigned long alloc_stack(int atomic);
extern void free_stack(unsigned long stack, int order);
struct pt_regs;