[CRIU] [PATCH v4] criu: fix filemap open permissions
Andrew Vagin
avagin at parallels.com
Fri Apr 4 10:25:41 PDT 2014
On Fri, Apr 04, 2014 at 12:36:39PM +0400, Andrew Vagin wrote:
> On Fri, Apr 04, 2014 at 01:04:08AM -0700, Jamie Liu wrote:
> > An mmaped file is opened O_RDONLY or O_RDWR depending on the permissions
> > on the first vma dump_task_mm() encounters mapping that file. This
> > causes two problems:
> >
> > 1. If a file has multiple MAP_SHARED mappings, some of which are
> > read-only and some of which are read-write, and the first encountered
> > mapping happens to be read-only, the file will be opened O_RDONLY
> > during restore, and mmap(PROT_WRITE) will fail with EACCES, causing
> > the restore to fail.
> >
> > 2. If a file is opened read-write and mapped read-only, it will be
> > opened O_RDONLY during restore, so restore will succeed, but
> > mprotect(PROT_WRITE) on the read-only mapping after restore will
> > fail.
> >
> > To fix both of these, record open flags per-vma based on the presence of
> > VM_MAYWRITE in smaps.
> >
> > Signed-off-by: Jamie Liu <jamieliu at google.com>
> > ---
> > cr-dump.c | 6 +-----
> > files-reg.c | 9 +++++++++
> > proc_parse.c | 14 ++++++++++++++
> > protobuf/vma.proto | 3 +++
> > 4 files changed, 27 insertions(+), 5 deletions(-)
> >
> > diff --git a/cr-dump.c b/cr-dump.c
> > index 0111115..258ba4b 100644
> > --- a/cr-dump.c
> > +++ b/cr-dump.c
> > @@ -15,7 +15,6 @@
> > #include <sys/vfs.h>
> >
> > #include <sys/sendfile.h>
> > -#include <sys/mman.h>
> >
> > #include <sched.h>
> > #include <sys/resource.h>
> > @@ -347,10 +346,7 @@ static int dump_filemap(pid_t pid, struct vma_area *vma_area,
> > BUG_ON(!vma_area->st);
> > p.stat = *vma_area->st;
> >
> > - if ((vma->prot & PROT_WRITE) && vma_entry_is(vma, VMA_FILE_SHARED))
> > - p.flags = O_RDWR;
> > - else
> > - p.flags = O_RDONLY;
> > + /* Flags will be set during restore in get_filemap_fd() */
> >
> > if (fd_id_generate_special(&p.stat, &id))
> > ret = dump_one_reg_file(vma_area->vm_file_fd, id, &p);
> > diff --git a/files-reg.c b/files-reg.c
> > index eccd04e..57312f9 100644
> > --- a/files-reg.c
> > +++ b/files-reg.c
> > @@ -708,6 +708,8 @@ int open_reg_by_id(u32 id)
> >
> > int get_filemap_fd(struct vma_area *vma)
> > {
> > + struct reg_file_info *rfi;
> > +
> > /*
> > * Thevma->fd should have been assigned in collect_filemap
> > *
> > @@ -715,6 +717,13 @@ int get_filemap_fd(struct vma_area *vma)
> > */
> >
> > BUG_ON(vma->fd == NULL);
> > + rfi = container_of(vma->fd, struct reg_file_info, d);
> > + if (vma->e->has_fdflags)
> > + rfi->rfe->flags = vma->e->fdflags;
> > + else {
> > + pr_err("vma %#lx missing fdflags", vma->e->start);
>
> Are you going to break backward compatibility?
Sorry for this short and rude comment.
I wanted to say that criu should able to restore processes from old images.
You can use zdtm to check compatibility:
[root at avagin-fc19-cr crtools]# bash test/zdtm.sh -b v1.2 static/maps00
make[1]: `built-in.o' is up to date.
make[1]: `lib/libcriu.so' is up to date.
make[2]: `arch/x86/syscalls.built-in.o' is up to date.
make[2]: `arch/x86/crtools.built-in.o' is up to date.
make[2]: `pie/util-fd.o' is up to date.
make[2]: `pie/util.o' is up to date.
make[2]: `arch/x86/vdso-pie.o' is up to date.
make[2]: `built-in.o' is up to date.
================================= CRIU CHECK =================================
Looks good.
Execute zdtm/live/static/maps00
./maps00 --pidfile=maps00.pid --outfile=maps00.out --filename=maps00.test
Dump 26910
Restore
Test: zdtm/live/static/maps00, Result: FAIL
==================================== ERROR ====================================
Test: zdtm/live/static/maps00, Namespace:
Dump log : /root/git/crtools/test/dump/maps00/26910/1/dump.log
--------------------------------- grep Error ---------------------------------
(00.001400) Error (image.c:197): Unable to open irmap-cache: No such file or directory
------------------------------------- END -------------------------------------
Restore log: /root/git/crtools/test/dump/maps00/26910/1/restore.log
--------------------------------- grep Error ---------------------------------
(00.021803) 26910: Error (files-reg.c:724): vma 0x400000 missing fdflags(00.021837) 26910: Error (cr-restore.c:231): Can't fixup VMA's fd
(00.022950) Error (cr-restore.c:1036): 26910 exited, status=1
(00.023051) Error (cr-restore.c:1579): Restoring FAILED.
------------------------------------- END -------------------------------------
================================= ERROR OVER =================================
If you have time, could you fix this issue?
Thanks.
> > + rturn -1;
> > + }
> > return open_path(vma->fd, do_open_reg_noseek, NULL);
> > }
> >
> > diff --git a/proc_parse.c b/proc_parse.c
> > index d628e81..b8dce14 100644
> > --- a/proc_parse.c
> > +++ b/proc_parse.c
> > @@ -92,6 +92,8 @@ static bool is_vma_range_fmt(char *line)
> > static int parse_vmflags(char *buf, struct vma_area *vma_area)
> > {
> > char *tok;
> > + bool shared = false;
> > + bool maywrite = false;
> >
> > if (!buf[0])
> > return 0;
> > @@ -103,6 +105,12 @@ static int parse_vmflags(char *buf, struct vma_area *vma_area)
> > #define _vmflag_match(_t, _s) (_t[0] == _s[0] && _t[1] == _s[1])
> >
> > do {
> > + /* open() block */
> > + if (_vmflag_match(tok, "sh"))
> > + shared = true;
> > + else if (_vmflag_match(tok, "mw"))
> > + maywrite = true;
> > +
> > /* mmap() block */
> > if (_vmflag_match(tok, "gd"))
> > vma_area->e->flags |= MAP_GROWSDOWN;
> > @@ -136,6 +144,12 @@ static int parse_vmflags(char *buf, struct vma_area *vma_area)
> >
> > #undef _vmflag_match
> >
> > + if (shared && maywrite)
> > + vma_area->e->fdflags = O_RDWR;
> > + else
> > + vma_area->e->fdflags = O_RDONLY;
> > + vma_area->e->has_fdflags = true;
> > +
> > if (vma_area->e->madv)
> > vma_area->e->has_madv = true;
> >
> > diff --git a/protobuf/vma.proto b/protobuf/vma.proto
> > index 8100965..af88807 100644
> > --- a/protobuf/vma.proto
> > +++ b/protobuf/vma.proto
> > @@ -15,4 +15,7 @@ message vma_entry {
> >
> > /* madvise flags bitmap */
> > optional uint64 madv = 9;
> > +
> > + /* file status flags */
> > + optional uint32 fdflags = 10;
> > }
> > --
> > 1.9.1.423.g4596e3a
> >
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