Peter Maydell <[email protected]> writes:
> On Mon, 27 Jul 2020 at 13:24, Alex Bennée <[email protected]> wrote: >> >> Plain MAP_FIXED has the undesirable behaviour of splatting exiting >> maps so we don't actually achieve what we want when looking for gaps. >> We should be using MAP_FIXED_NOREPLACE. As this isn't always available >> we need to potentially check the returned address to see if the kernel >> gave us what we asked for. >> >> Fixes: ad592e37dfc ("linux-user: provide fallback pgd_find_hole for bare >> chroots") >> Signed-off-by: Alex Bennée <[email protected]> >> Reviewed-by: Richard Henderson <[email protected]> >> Message-Id: <[email protected]> > > Hi; Coverity thinks this conditional expression is suspicious > (CID 1431059): > >> if (mmap_start != MAP_FAILED) { >> munmap((void *) align_start, guest_size); >> - return (uintptr_t) mmap_start + offset; >> + if (MAP_FIXED_NOREPLACE || mmap_start == (void *) >> align_start) { > > because it's performing a logical OR operation where the left > operand is an integer constant that's neither 0 nor 1 > (it's 1048576). What was this intended to be? It's 0 if the header doesn't provide it. If it's !0 we don't need to check the address because it should have been in the correct place. > >> + return (uintptr_t) mmap_start + offset; >> + } >> } > > thanks > -- PMM -- Alex Bennée
