Messages in this thread | | | Date | Tue, 17 Dec 2019 10:28:31 +0000 | From | Russell King - ARM Linux admin <> | Subject | Re: [PATCH] asm/sections: Check for overflow in memory_contains() |
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On Tue, Dec 17, 2019 at 11:22:38AM +0100, Vincent Whitchurch wrote: > ARM uses memory_contains() from its stacktrace code via this function: > > static inline bool in_entry_text(unsigned long addr) > { > return memory_contains(__entry_text_start, __entry_text_end, > (void *)addr, 1); > } > > addr is taken from the stack and can be a completely invalid. If addr > is 0xffffffff, there is an overflow in the pointer arithmetic in > memory_contains() and in_entry_text() incorrectly returns true. > > Fix this by adding an overflow check. The check is done on unsigned > longs to avoid undefined behaviour. > > Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com> > --- > include/asm-generic/sections.h | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h > index d1779d442aa5..e6e1b381c5df 100644 > --- a/include/asm-generic/sections.h > +++ b/include/asm-generic/sections.h > @@ -105,7 +105,15 @@ static inline int arch_is_kernel_initmem_freed(unsigned long addr) > static inline bool memory_contains(void *begin, void *end, void *virt, > size_t size) > { > - return virt >= begin && virt + size <= end; > + unsigned long membegin = (unsigned long)begin; > + unsigned long memend = (unsigned long)end; > + unsigned long objbegin = (unsigned long)virt; > + unsigned long objend = objbegin + size; > + > + if (objend < objbegin) > + return false; > + > + return objbegin >= membegin && objend <= memend;
Would merely changing to:
return virt >= begin && virt <= end - size;
be sufficient ? Is end - size possible to underflow?
> } > > /** > -- > 2.20.0 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
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