[CRIU] [PATCH] proc_parse: fix vma file open mode recognition
Stanislav Kinsburskiy
skinsbursky at virtuozzo.com
Mon Jul 4 11:59:46 PDT 2016
4 июля 2016 г. 20:05 пользователь Pavel Emelianov <xemul at virtuozzo.com> написал:
>
> On 06/30/2016 07:24 PM, Stanislav Kinsburskiy wrote:
> > The correct place to get fd open flags for file mappings is
> > /proc/<pid>/map_files.
> > An attempt tp speculate on "shared" and "maywrite" bits doesn't garantee,
> > that file will be opened with correct permissions on restore.
> > Here is an example:
> >
> > Process mapping (read/write):
> >
> > # cat /proc/481943/maps | grep 7f7108077000-7f7108078000
> > 7f7108077000-7f7108078000 rw-p 00001000 00:35 7 <snip>
> >
> > 1) Before suspend:
> >
> > # ls -l /proc/481427/map_files/7f7108077000-7f7108078000
> > lrw------- <snip> /proc/481427/map_files/7f7108077000-7f7108078000 -> <snip>
> >
> > 2) After restore:
> >
> > # ls -l /proc/481943/map_files/7f7108077000-7f7108078000
> > lr-------- <snip> /proc/481943/map_files/7f7108077000-7f7108078000 -> <snip>
> >
> > Write bit is lost.
> >
> > This patch set vma->e->fdflags as /proc/<pid>/map_files/<vma> open mode.
> >
> > Signed-off-by: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
> > ---
> > criu/proc_parse.c | 51 ++++++++++++++++++++++++++++++++++-----------------
> > criu/util.c | 3 ++-
> > 2 files changed, 36 insertions(+), 18 deletions(-)
> >
> > diff --git a/criu/proc_parse.c b/criu/proc_parse.c
> > index 5210226..8e36916 100644
> > --- a/criu/proc_parse.c
> > +++ b/criu/proc_parse.c
> > @@ -82,8 +82,6 @@ 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;
> > @@ -95,12 +93,6 @@ 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;
> > @@ -144,12 +136,6 @@ 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;
> >
> > @@ -175,12 +161,46 @@ static inline int vfi_equal(struct vma_file_info *a, struct vma_file_info *b)
> > (a->dev_min ^ b->dev_min)) == 0;
> > }
> >
> > +static int vma_get_mapfile_flags(struct vma_area *vma, DIR *mfd, char *path)
> > +{
> > + struct stat stat;
> > +
> > + if (fstatat(dirfd(mfd), path, &stat, AT_SYMLINK_NOFOLLOW) < 0) {
> > + if (errno == ENOENT) {
> > + /* Just mapping w/o map_files link */
> > + return 0;
> > + }
> > + pr_perror("Failed fstatat on map %"PRIx64"", vma->e->start);
> > + return -1;
> > + }
> > +
> > + switch(stat.st_mode & 0600) {
> > + case 0200:
> > + vma->e->fdflags = O_WRONLY;
> > + break;
> > + case 0400:
> > + vma->e->fdflags = O_RDONLY;
> > + break;
> > + case 0600:
> > + vma->e->fdflags = O_RDWR;
> > + break;
> > + }
> > + vma->e->has_fdflags = true;
> > + return 0;
> > +}
> > +
> > static int vma_get_mapfile(char *fname, struct vma_area *vma, DIR *mfd,
> > struct vma_file_info *vfi, struct vma_file_info *prev_vfi)
> > {
> > char path[32];
> > int flags;
> >
> > + /* Figure out if it's file mapping */
> > + snprintf(path, sizeof(path), "%"PRIx64"-%"PRIx64, vma->e->start, vma->e->end);
> > +
> > + if (vma_get_mapfile_flags(vma, mfd, path))
> > + return -1;
>
> Can we re-use the vmfd borrowing logic for fdflags too?
>
You mean in the cycle below?
Yes, but then we have to add check for fdflags to vfi_equal, shouldn't we?
> > +
> > if (prev_vfi->vma && vfi_equal(vfi, prev_vfi)) {
> > struct vma_area *prev = prev_vfi->vma;
> >
> > @@ -209,9 +229,6 @@ static int vma_get_mapfile(char *fname, struct vma_area *vma, DIR *mfd,
> > return 0;
> > }
> >
> > - /* Figure out if it's file mapping */
> > - snprintf(path, sizeof(path), "%"PRIx64"-%"PRIx64, vma->e->start, vma->e->end);
> > -
> > /*
> > * Note that we "open" it in dumper process space
> > * so later we might refer to it via /proc/self/fd/vm_file_fd
> > diff --git a/criu/util.c b/criu/util.c
> > index e8ebe61..07bc16e 100644
> > --- a/criu/util.c
> > +++ b/criu/util.c
> > @@ -161,12 +161,13 @@ void pr_vma(unsigned int loglevel, const struct vma_area *vma_area)
> > return;
> >
> > vma_opt_str(vma_area, opt);
> > - print_on_level(loglevel, "%#"PRIx64"-%#"PRIx64" (%"PRIi64"K) prot %#x flags %#x st %#x off %#"PRIx64" "
> > + print_on_level(loglevel, "%#"PRIx64"-%#"PRIx64" (%"PRIi64"K) prot %#x flags %#x fdflags %#o st %#x off %#"PRIx64" "
> > "%s shmid: %#"PRIx64"\n",
> > vma_area->e->start, vma_area->e->end,
> > KBYTES(vma_area_len(vma_area)),
> > vma_area->e->prot,
> > vma_area->e->flags,
> > + vma_area->e->fdflags,
> > vma_area->e->status,
> > vma_area->e->pgoff,
> > opt, vma_area->e->shmid);
> >
> > _______________________________________________
> > CRIU mailing list
> > CRIU at openvz.org
> > https://lists.openvz.org/mailman/listinfo/criu
> > .
> >
>
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