[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] libxc: check return values on mmap() and madvise() on xc_alloc_hypercall_buffer()
Please backport this patch to 4.4. Other branches may need the mmap() check as well. The callers expect either NULL or a valid pointer. It is upstream commit e86539a388314cd3dca88f5e69d7873343197cd8 Thanks, Olaf On Wed, May 21, Ian Campbell wrote: > On Tue, 2014-05-20 at 05:37 -0700, Luis R. Rodriguez wrote: > > From: "Luis R. Rodriguez" <mcgrof@xxxxxxxx> > > > > On a Thinkpad T4440p with OpenSUSE tumbleweed with v3.15-rc4 > > and today's latest xen tip from the git tree strace -f reveals > > we end up on a never ending wait shortly after > > > > write(20, "backend/console/5\0", 18 <unfinished ...> > > > > This is right before we just wait on the qemu process which we > > had mmap'd for. Without this you'll end up getting stuck on a > > loop if mmap() worked but madvise() did not. While at it I noticed > > even the mmap() error fail was not being checked, fix that too. > > > > Signed-off-by: Luis R. Rodriguez <mcgrof@xxxxxxxx> > > Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx> and applied. > > OOI why was madvise failing? (should be quite unusual I think?) > > > --- > > tools/libxc/xc_linux_osdep.c | 20 +++++++++++++++++++- > > 1 file changed, 19 insertions(+), 1 deletion(-) > > > > diff --git a/tools/libxc/xc_linux_osdep.c b/tools/libxc/xc_linux_osdep.c > > index 73860a2..86bff3e 100644 > > --- a/tools/libxc/xc_linux_osdep.c > > +++ b/tools/libxc/xc_linux_osdep.c > > @@ -92,14 +92,32 @@ static void > > *linux_privcmd_alloc_hypercall_buffer(xc_interface *xch, xc_osdep_ha > > { > > size_t size = npages * XC_PAGE_SIZE; > > void *p; > > + int rc, saved_errno; > > > > /* Address returned by mmap is page aligned. */ > > p = mmap(NULL, size, PROT_READ|PROT_WRITE, > > MAP_PRIVATE|MAP_ANONYMOUS|MAP_LOCKED, -1, 0); > > + if ( p == MAP_FAILED ) > > + { > > + PERROR("xc_alloc_hypercall_buffer: mmap failed"); > > + return NULL; > > + } > > > > /* Do not copy the VMA to child process on fork. Avoid the page being > > COW > > on hypercall. */ > > - madvise(p, npages * XC_PAGE_SIZE, MADV_DONTFORK); > > + rc = madvise(p, npages * XC_PAGE_SIZE, MADV_DONTFORK); > > + if ( rc < 0 ) > > + { > > + PERROR("xc_alloc_hypercall_buffer: madvise failed"); > > + goto out; > > + } > > + > > return p; > > + > > +out: > > + saved_errno = errno; > > + (void)munmap(p, size); > > + errno = saved_errno; > > + return NULL; > > } > > > > static void linux_privcmd_free_hypercall_buffer(xc_interface *xch, > > xc_osdep_handle h, void *ptr, int npages) _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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