Le 13/02/2024 à 05:36, Benjamin Gray a écrit : > The memset/memcpy functions are by default instrumented by KASAN, which > complains about user memory access when using a poking page in > userspace. > > Using a userspace address is expected though, so don't instrument with > KASAN for this function.
memcpy/memset should never be used to access user memory, we have copy_to_user() and clear_user() for that. A few weeks age I sent a KASAN report I got from the same function. But I got it on PPC32 which doesn't use userspace for that. See https://lore.kernel.org/all/2000a30f-214a-4b20-b0b5-348e987d6...@csgroup.eu/T/#u So I have the feeling that your patch may be hidding another problem. The PPC32 report for sure will be hidden if your patch gets applied, allthough your explanation doesn't fit. Christophe > > Signed-off-by: Benjamin Gray <bg...@linux.ibm.com> > > --- > > I tried to replace the memsetN calls with __memsetN, but we appear to > disable the non-instrumented variants of these when KASAN is enabled. > Christophe might you know more here? > > The cost of just suppressing reports for this section shouldn't be too > relevant; KASAN detects the access, but exits before it starts preparing > the report itself. So it's just like any other KASAN instrumented > function for the most part. > --- > arch/powerpc/lib/code-patching.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/powerpc/lib/code-patching.c > b/arch/powerpc/lib/code-patching.c > index c6ab46156cda..24989594578a 100644 > --- a/arch/powerpc/lib/code-patching.c > +++ b/arch/powerpc/lib/code-patching.c > @@ -3,6 +3,7 @@ > * Copyright 2008 Michael Ellerman, IBM Corporation. > */ > > +#include <linux/kasan.h> > #include <linux/kprobes.h> > #include <linux/mmu_context.h> > #include <linux/random.h> > @@ -377,6 +378,7 @@ static int __patch_instructions(u32 *patch_addr, u32 > *code, size_t len, bool rep > unsigned long start = (unsigned long)patch_addr; > > /* Repeat instruction */ > + kasan_disable_current(); > if (repeat_instr) { > ppc_inst_t instr = ppc_inst_read(code); > > @@ -392,6 +394,7 @@ static int __patch_instructions(u32 *patch_addr, u32 > *code, size_t len, bool rep > } else { > memcpy(patch_addr, code, len); > } > + kasan_enable_current(); > > smp_wmb(); /* smp write barrier */ > flush_icache_range(start, start + len);
