Re: [PATCH] linux-user/elfload: munmap proper address in pgd_find_hole_fallback

[Vincent Fazio]

Pinging per Laurent.

On 2/14/21 5:32 AM, Alex Bennée wrote:
> Vincent Fazio <vfazio@xes-inc.com> writes:
>
> > From: Vincent Fazio <vfazio@gmail.com>
> >
> > Previously, if the build host's libc did not define MAP_FIXED_NOREPLACE
> > or if the running kernel didn't support that flag, it was possible for
> > pgd_find_hole_fallback to munmap an incorrect address which could lead to
> > SIGSEGV if the range happened to overlap with the mapped address of the
> > QEMU binary.
> >
> >    mmap(0x1000, 22261224, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, 
> > -1, 0) = 0x7f889d331000
> >    munmap(0x1000, 22261224)                = 0
> >    --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0x84b817} ---
> >    ++ killed by SIGSEGV +++
> >
> > Now, always munmap the address returned by mmap.
> >
> > Fixes: 2667e069e7b5 ("linux-user: don't use MAP_FIXED in 
> > pgd_find_hole_fallback")
> > Signed-off-by: Vincent Fazio <vfazio@gmail.com>
>
> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>