* [PATCH] fs/pnode.c: treat zero mnt_group_id-s as unequal @ 2016-02-16 19:45 Maxim Patlasov 2016-02-16 19:54 ` Al Viro 2016-02-16 22:58 ` Andrew Vagin 0 siblings, 2 replies; 5+ messages in thread From: Maxim Patlasov @ 2016-02-16 19:45 UTC (permalink / raw) To: viro; +Cc: linux-fsdevel, linux-kernel, devel propagate_one(m) calculates "type" argument for copy_tree() like this: > if (m->mnt_group_id == last_dest->mnt_group_id) { > type = CL_MAKE_SHARED; > } else { > type = CL_SLAVE; > if (IS_MNT_SHARED(m)) > type |= CL_MAKE_SHARED; > } The "type" argument then governs clone_mnt() behavior with respect to flags and mnt_master of new mount. When we iterate through a slave group, it is possible that both current "m" and "last_dest" are not shared (although, both are slaves, i.e. have non-NULL mnt_master-s). Then the comparison above erroneously makes new mount shared and sets its mnt_master to last_source->mnt_master. The patch fixes the problem by handling zero mnt_group_id-s as though they are unequal. The similar problem exists in the implementation of "else" clause above when we have to ascend upward in the master/slave tree by calling: > last_source = last_source->mnt_master; > last_dest = last_source->mnt_parent; proper number of times. The last step is governed by "n->mnt_group_id != last_dest->mnt_group_id" condition that may lie if both are zero. The patch fixes this case in the same way as the former one. Signed-off-by: Maxim Patlasov <mpatlasov@virtuozzo.com> --- fs/pnode.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/pnode.c b/fs/pnode.c index 6367e1e..abf156a 100644 --- a/fs/pnode.c +++ b/fs/pnode.c @@ -212,7 +212,7 @@ static int propagate_one(struct mount *m) /* skip if mountpoint isn't covered by it */ if (!is_subdir(mp->m_dentry, m->mnt.mnt_root)) return 0; - if (m->mnt_group_id == last_dest->mnt_group_id) { + if (m->mnt_group_id && m->mnt_group_id == last_dest->mnt_group_id) { type = CL_MAKE_SHARED; } else { struct mount *n, *p; @@ -223,7 +223,9 @@ static int propagate_one(struct mount *m) last_source = last_source->mnt_master; last_dest = last_source->mnt_parent; } - if (n->mnt_group_id != last_dest->mnt_group_id) { + if (n->mnt_group_id != last_dest->mnt_group_id || + (!n->mnt_group_id && + !last_dest->mnt_group_id)) { last_source = last_source->mnt_master; last_dest = last_source->mnt_parent; } ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] fs/pnode.c: treat zero mnt_group_id-s as unequal 2016-02-16 19:45 [PATCH] fs/pnode.c: treat zero mnt_group_id-s as unequal Maxim Patlasov @ 2016-02-16 19:54 ` Al Viro 2016-02-17 7:07 ` Maxim Patlasov 2016-02-16 22:58 ` Andrew Vagin 1 sibling, 1 reply; 5+ messages in thread From: Al Viro @ 2016-02-16 19:54 UTC (permalink / raw) To: Maxim Patlasov; +Cc: linux-fsdevel, linux-kernel, devel On Tue, Feb 16, 2016 at 11:45:33AM -0800, Maxim Patlasov wrote: > propagate_one(m) calculates "type" argument for copy_tree() like this: > > > if (m->mnt_group_id == last_dest->mnt_group_id) { > > type = CL_MAKE_SHARED; > > } else { > > type = CL_SLAVE; > > if (IS_MNT_SHARED(m)) > > type |= CL_MAKE_SHARED; > > } > > The "type" argument then governs clone_mnt() behavior with respect to flags > and mnt_master of new mount. When we iterate through a slave group, it is > possible that both current "m" and "last_dest" are not shared (although, > both are slaves, i.e. have non-NULL mnt_master-s). Then the comparison > above erroneously makes new mount shared and sets its mnt_master to > last_source->mnt_master. The patch fixes the problem by handling zero > mnt_group_id-s as though they are unequal. > > The similar problem exists in the implementation of "else" clause above > when we have to ascend upward in the master/slave tree by calling: > > > last_source = last_source->mnt_master; > > last_dest = last_source->mnt_parent; > > proper number of times. The last step is governed by > "n->mnt_group_id != last_dest->mnt_group_id" condition that may lie if > both are zero. The patch fixes this case in the same way as the former one. Mind putting together a reproducer? ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] fs/pnode.c: treat zero mnt_group_id-s as unequal 2016-02-16 19:54 ` Al Viro @ 2016-02-17 7:07 ` Maxim Patlasov 2016-02-26 0:26 ` [Devel] " Andrew Vagin 0 siblings, 1 reply; 5+ messages in thread From: Maxim Patlasov @ 2016-02-17 7:07 UTC (permalink / raw) To: Al Viro; +Cc: linux-fsdevel, linux-kernel, devel [-- Attachment #1: Type: text/plain, Size: 3220 bytes --] On 02/16/2016 11:54 AM, Al Viro wrote: > On Tue, Feb 16, 2016 at 11:45:33AM -0800, Maxim Patlasov wrote: >> propagate_one(m) calculates "type" argument for copy_tree() like this: >> >>> if (m->mnt_group_id == last_dest->mnt_group_id) { >>> type = CL_MAKE_SHARED; >>> } else { >>> type = CL_SLAVE; >>> if (IS_MNT_SHARED(m)) >>> type |= CL_MAKE_SHARED; >>> } >> The "type" argument then governs clone_mnt() behavior with respect to flags >> and mnt_master of new mount. When we iterate through a slave group, it is >> possible that both current "m" and "last_dest" are not shared (although, >> both are slaves, i.e. have non-NULL mnt_master-s). Then the comparison >> above erroneously makes new mount shared and sets its mnt_master to >> last_source->mnt_master. The patch fixes the problem by handling zero >> mnt_group_id-s as though they are unequal. >> >> The similar problem exists in the implementation of "else" clause above >> when we have to ascend upward in the master/slave tree by calling: >> >>> last_source = last_source->mnt_master; >>> last_dest = last_source->mnt_parent; >> proper number of times. The last step is governed by >> "n->mnt_group_id != last_dest->mnt_group_id" condition that may lie if >> both are zero. The patch fixes this case in the same way as the former one. > Mind putting together a reproducer? There are two files attached: reproducer1.c and reproducer2.c. The former demonstrates the problem before applying the patch. The latter demonstrates why the first hunk of the patch is not enough. [root@f22ml ~]# reproducer1 main pid = 1496 monitor pid = 1497 child pid = 1498 grand-child pid = 1499 [root@f22ml ~]# grep "child" /proc/1496/mountinfo 243 144 0:37 /child /tmp/child rw shared:93 - tmpfs tmpfs rw,seclabel [root@f22ml ~]# grep "child" /proc/1498/mountinfo 244 208 0:37 /child /tmp/child rw shared:127 master:93 - tmpfs tmpfs rw,seclabel [root@f22ml ~]# grep "child" /proc/1499/mountinfo 245 240 0:37 /child /tmp/child rw master:127 - tmpfs tmpfs rw,seclabel [root@f22ml ~]# grep "child" /proc/1497/mountinfo 246 176 0:37 /child /tmp/child rw shared:128 master:127 - tmpfs tmpfs rw,seclabel while expected info for 1497 would be: 246 176 0:37 /child /tmp/child rw master:93 - tmpfs tmpfs rw,seclabel Now, assuming that only the first hunk of the patch is applied: > - if (m->mnt_group_id == last_dest->mnt_group_id) { > + if (m->mnt_group_id && m->mnt_group_id == last_dest->mnt_group_id) { [root@f22ml ~]# reproducer2 main pid = 1506 monitor pid = 1507 child pid = 1508 grand-child pid = 1509 [root@f22ml ~]# grep "child" /proc/1506/mountinfo 243 144 0:37 /child /tmp/child rw shared:93 - tmpfs tmpfs rw,seclabel [root@f22ml ~]# grep "child" /proc/1508/mountinfo 244 208 0:37 /child /tmp/child rw shared:93 - tmpfs tmpfs rw,seclabel [root@f22ml ~]# grep "child" /proc/1509/mountinfo 245 240 0:37 /child /tmp/child rw master:93 - tmpfs tmpfs rw,seclabel [root@f22ml ~]# grep "child" /proc/1507/mountinfo 246 176 0:37 /child /tmp/child rw master:0 - tmpfs tmpfs rw,seclabel while expected info for 1507 would be: 246 176 0:37 /child /tmp/child rw master:93 - tmpfs tmpfs rw,seclabel Thanks, Maxim [-- Attachment #2: reproducer1.c --] [-- Type: text/x-csrc, Size: 2440 bytes --] #define _GNU_SOURCE #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <sys/stat.h> #include <sys/types.h> #include <errno.h> #include <sys/mount.h> #include <sys/syscall.h> #include <sched.h> int main() { const char *child = "/tmp/child"; int ret; printf("main pid = %d\n", getpid()); /* make our own private playground ... */ ret = unshare(CLONE_NEWNS); if (ret) { perror("unshare"); exit(1); } ret = mount("none", "/", NULL, MS_REC|MS_PRIVATE, NULL); if (ret) { perror("mount"); exit(1); } ret = mount("none", "/", NULL, MS_REC|MS_SHARED, NULL); if (ret) { perror("mount2"); exit(1); } /* fork monitor ... */ ret = fork(); if (ret < 0) { perror("fork"); exit(1); } else if (!ret) { printf("monitor pid = %d\n", getpid()); ret = unshare(CLONE_NEWNS); if (ret) { perror("unshare in monitor"); exit(1); } ret = mount("none", "/", NULL, MS_REC|MS_SHARED, NULL); if (ret) { perror("mount in monitor"); exit(1); } ret = mount("none", "/", NULL, MS_REC|MS_SLAVE, NULL); if (ret) { perror("mount2 in monitor"); exit(1); } sleep(-1); } /* wait monitor to setup */ sleep(1); /* fork child ... */ ret = fork(); if (ret < 0) { perror("fork"); exit(1); } else if (!ret) { printf("child pid = %d\n", getpid()); ret = unshare(CLONE_NEWNS); if (ret) { perror("unshare in child"); exit(1); } ret = mount("none", "/", NULL, MS_REC|MS_SLAVE, NULL); if (ret) { perror("mount in child"); exit(1); } ret = mount(NULL, "/", NULL, MS_REC|MS_SHARED, NULL); if (ret) { perror("mount2 in child"); exit(1); } if (!fork()) { /* grand-child */ printf("grand-child pid = %d\n", getpid()); ret = unshare(CLONE_NEWNS); if (ret) { perror("unshare in grand-child"); exit(1); } ret = mount("none", "/", NULL, MS_REC|MS_SHARED, NULL); if (ret) { perror("mount in grand-child"); exit(1); } ret = mount("none", "/", NULL, MS_REC|MS_SLAVE, NULL); if (ret) { perror("mount2 in grand-child"); exit(1); } sleep(-1); } sleep(-1); } /* wait child and grand-child to setup */ sleep(1); ret = mkdir(child, 0755); if (ret && errno != EEXIST) { perror("mkdir"); exit(1); } /* let "child" mount slip to everyone' namespaces ... */ ret = mount(child, child, NULL, MS_BIND, NULL); if (ret) { perror("bind mount"); exit(1); } sleep(-1); } [-- Attachment #3: reproducer2.c --] [-- Type: text/x-csrc, Size: 2209 bytes --] #define _GNU_SOURCE #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <sys/stat.h> #include <sys/types.h> #include <errno.h> #include <sys/mount.h> #include <sys/syscall.h> #include <sched.h> int main() { const char *child = "/tmp/child"; int ret; printf("main pid = %d\n", getpid()); /* make our own private playground ... */ ret = unshare(CLONE_NEWNS); if (ret) { perror("unshare"); exit(1); } ret = mount("none", "/", NULL, MS_REC|MS_PRIVATE, NULL); if (ret) { perror("mount"); exit(1); } ret = mount("none", "/", NULL, MS_REC|MS_SHARED, NULL); if (ret) { perror("mount2"); exit(1); } /* fork monitor ... */ ret = fork(); if (ret < 0) { perror("fork"); exit(1); } else if (!ret) { printf("monitor pid = %d\n", getpid()); ret = unshare(CLONE_NEWNS); if (ret) { perror("unshare in monitor"); exit(1); } ret = mount("none", "/", NULL, MS_REC|MS_SHARED, NULL); if (ret) { perror("mount in monitor"); exit(1); } ret = mount("none", "/", NULL, MS_REC|MS_SLAVE, NULL); if (ret) { perror("mount2 in monitor"); exit(1); } sleep(-1); } /* wait monitor to setup */ sleep(1); /* fork child ... */ ret = fork(); if (ret < 0) { perror("fork"); exit(1); } else if (!ret) { printf("child pid = %d\n", getpid()); ret = unshare(CLONE_NEWNS); if (ret) { perror("unshare in child"); exit(1); } if (!fork()) { /* grand-child */ printf("grand-child pid = %d\n", getpid()); ret = unshare(CLONE_NEWNS); if (ret) { perror("unshare in grand-child"); exit(1); } ret = mount("none", "/", NULL, MS_REC|MS_SHARED, NULL); if (ret) { perror("mount in grand-child"); exit(1); } ret = mount("none", "/", NULL, MS_REC|MS_SLAVE, NULL); if (ret) { perror("mount2 in grand-child"); exit(1); } sleep(-1); } sleep(-1); } /* wait child and grand-child to setup */ sleep(1); ret = mkdir(child, 0755); if (ret && errno != EEXIST) { perror("mkdir"); exit(1); } /* let "child" mount slip to everyone' namespaces ... */ ret = mount(child, child, NULL, MS_BIND, NULL); if (ret) { perror("bind mount"); exit(1); } sleep(-1); } ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Devel] [PATCH] fs/pnode.c: treat zero mnt_group_id-s as unequal 2016-02-17 7:07 ` Maxim Patlasov @ 2016-02-26 0:26 ` Andrew Vagin 0 siblings, 0 replies; 5+ messages in thread From: Andrew Vagin @ 2016-02-26 0:26 UTC (permalink / raw) To: Maxim Patlasov; +Cc: Al Viro, linux-fsdevel, linux-kernel, devel On Tue, Feb 16, 2016 at 11:07:32PM -0800, Maxim Patlasov wrote: > On 02/16/2016 11:54 AM, Al Viro wrote: > >On Tue, Feb 16, 2016 at 11:45:33AM -0800, Maxim Patlasov wrote: > >>propagate_one(m) calculates "type" argument for copy_tree() like this: > >> > >>> if (m->mnt_group_id == last_dest->mnt_group_id) { > >>> type = CL_MAKE_SHARED; > >>> } else { > >>> type = CL_SLAVE; > >>> if (IS_MNT_SHARED(m)) > >>> type |= CL_MAKE_SHARED; > >>> } > >>The "type" argument then governs clone_mnt() behavior with respect to flags > >>and mnt_master of new mount. When we iterate through a slave group, it is > >>possible that both current "m" and "last_dest" are not shared (although, > >>both are slaves, i.e. have non-NULL mnt_master-s). Then the comparison > >>above erroneously makes new mount shared and sets its mnt_master to > >>last_source->mnt_master. The patch fixes the problem by handling zero > >>mnt_group_id-s as though they are unequal. > >> > >>The similar problem exists in the implementation of "else" clause above > >>when we have to ascend upward in the master/slave tree by calling: > >> > >>> last_source = last_source->mnt_master; > >>> last_dest = last_source->mnt_parent; > >>proper number of times. The last step is governed by > >>"n->mnt_group_id != last_dest->mnt_group_id" condition that may lie if > >>both are zero. The patch fixes this case in the same way as the former one. > >Mind putting together a reproducer? > > There are two files attached: reproducer1.c and reproducer2.c. The former > demonstrates the problem before applying the patch. The latter demonstrates > why the first hunk of the patch is not enough. > > [root@f22ml ~]# reproducer1 > main pid = 1496 > monitor pid = 1497 > child pid = 1498 > grand-child pid = 1499 > > [root@f22ml ~]# grep "child" /proc/1496/mountinfo > 243 144 0:37 /child /tmp/child rw shared:93 - tmpfs tmpfs rw,seclabel > [root@f22ml ~]# grep "child" /proc/1498/mountinfo > 244 208 0:37 /child /tmp/child rw shared:127 master:93 - tmpfs tmpfs > rw,seclabel > [root@f22ml ~]# grep "child" /proc/1499/mountinfo > 245 240 0:37 /child /tmp/child rw master:127 - tmpfs tmpfs rw,seclabel > [root@f22ml ~]# grep "child" /proc/1497/mountinfo > 246 176 0:37 /child /tmp/child rw shared:128 master:127 - tmpfs tmpfs > rw,seclabel > > while expected info for 1497 would be: > 246 176 0:37 /child /tmp/child rw master:93 - tmpfs tmpfs rw,seclabel > Here is a simpler reproducer without additional namespaces and processes. [root@fc22-vm tmp]# cat test.sh set -e d=`pwd` mount -t tmpfs test $d cd $d mkdir root mount -t tmpfs root root mount --make-shared root mkdir monitor mount --bind root monitor/ mount --make-slave monitor/ mkdir child mount --bind root child/ mount --make-slave child mount --make-shared child/ mkdir grand_child mount --bind child grand_child mount --make-slave grand_child mkdir root/test mount --bind root/test root/test cat /proc/self/mountinfo | grep $d echo --- cat /proc/self/mountinfo | grep monitor/test | grep shared && echo FAIL || echo PASS exit [root@fc22-vm tmp]# bash test.sh 80 61 0:41 / /root/tmp rw,relatime shared:32 - tmpfs test rw 82 80 0:42 / /root/tmp/root rw,relatime shared:33 - tmpfs root rw 84 80 0:42 / /root/tmp/monitor rw,relatime master:33 - tmpfs root rw 86 80 0:42 / /root/tmp/child rw,relatime shared:34 master:33 - tmpfs root rw 88 80 0:42 / /root/tmp/grand_child rw,relatime master:34 - tmpfs root rw 90 82 0:42 /test /root/tmp/root/test rw,relatime shared:33 - tmpfs root rw 94 84 0:42 /test /root/tmp/monitor/test rw,relatime shared:36 master:35 - tmpfs root rw 92 88 0:42 /test /root/tmp/grand_child/test rw,relatime master:35 - tmpfs root rw 91 86 0:42 /test /root/tmp/child/test rw,relatime shared:35 master:33 - tmpfs root rw --- 94 84 0:42 /test /root/tmp/monitor/test rw,relatime shared:36 master:35 - tmpfs root rw FAIL > Now, assuming that only the first hunk of the patch is applied: > > > - if (m->mnt_group_id == last_dest->mnt_group_id) { > > + if (m->mnt_group_id && m->mnt_group_id == last_dest->mnt_group_id) { > > [root@f22ml ~]# reproducer2 > main pid = 1506 > monitor pid = 1507 > child pid = 1508 > grand-child pid = 1509 > > [root@f22ml ~]# grep "child" /proc/1506/mountinfo > 243 144 0:37 /child /tmp/child rw shared:93 - tmpfs tmpfs rw,seclabel > [root@f22ml ~]# grep "child" /proc/1508/mountinfo > 244 208 0:37 /child /tmp/child rw shared:93 - tmpfs tmpfs rw,seclabel > [root@f22ml ~]# grep "child" /proc/1509/mountinfo > 245 240 0:37 /child /tmp/child rw master:93 - tmpfs tmpfs rw,seclabel > [root@f22ml ~]# grep "child" /proc/1507/mountinfo > 246 176 0:37 /child /tmp/child rw master:0 - tmpfs tmpfs rw,seclabel > > while expected info for 1507 would be: > 246 176 0:37 /child /tmp/child rw master:93 - tmpfs tmpfs rw,seclabel > > Thanks, > Maxim > #define _GNU_SOURCE > #include <stdio.h> > #include <unistd.h> > #include <stdlib.h> > #include <sys/stat.h> > #include <sys/types.h> > #include <errno.h> > #include <sys/mount.h> > #include <sys/syscall.h> > #include <sched.h> > > int main() > { > const char *child = "/tmp/child"; > int ret; > > printf("main pid = %d\n", getpid()); > > /* make our own private playground ... */ > ret = unshare(CLONE_NEWNS); > if (ret) { > perror("unshare"); > exit(1); > } > > ret = mount("none", "/", NULL, MS_REC|MS_PRIVATE, NULL); > if (ret) { > perror("mount"); > exit(1); > } > > ret = mount("none", "/", NULL, MS_REC|MS_SHARED, NULL); > if (ret) { > perror("mount2"); > exit(1); > } > > /* fork monitor ... */ > ret = fork(); > if (ret < 0) { > perror("fork"); > exit(1); > } else if (!ret) { > printf("monitor pid = %d\n", getpid()); > > ret = unshare(CLONE_NEWNS); > if (ret) { > perror("unshare in monitor"); > exit(1); > } > > ret = mount("none", "/", NULL, MS_REC|MS_SHARED, NULL); > if (ret) { > perror("mount in monitor"); > exit(1); > } > > ret = mount("none", "/", NULL, MS_REC|MS_SLAVE, NULL); > if (ret) { > perror("mount2 in monitor"); > exit(1); > } > > sleep(-1); > } > > /* wait monitor to setup */ > sleep(1); > > > /* fork child ... */ > ret = fork(); > if (ret < 0) { > perror("fork"); > exit(1); > } else if (!ret) { > printf("child pid = %d\n", getpid()); > > ret = unshare(CLONE_NEWNS); > if (ret) { > perror("unshare in child"); > exit(1); > } > > ret = mount("none", "/", NULL, MS_REC|MS_SLAVE, NULL); > if (ret) { > perror("mount in child"); > exit(1); > } > ret = mount(NULL, "/", NULL, MS_REC|MS_SHARED, NULL); > if (ret) { > perror("mount2 in child"); > exit(1); > } > > if (!fork()) { /* grand-child */ > printf("grand-child pid = %d\n", getpid()); > ret = unshare(CLONE_NEWNS); > if (ret) { > perror("unshare in grand-child"); > exit(1); > } > > ret = mount("none", "/", NULL, MS_REC|MS_SHARED, NULL); > if (ret) { > perror("mount in grand-child"); > exit(1); > } > > ret = mount("none", "/", NULL, MS_REC|MS_SLAVE, NULL); > if (ret) { > perror("mount2 in grand-child"); > exit(1); > } > > sleep(-1); > } > > sleep(-1); > } > > /* wait child and grand-child to setup */ > sleep(1); > > ret = mkdir(child, 0755); > if (ret && errno != EEXIST) { > perror("mkdir"); > exit(1); > } > > /* let "child" mount slip to everyone' namespaces ... */ > ret = mount(child, child, NULL, MS_BIND, NULL); > if (ret) { > perror("bind mount"); > exit(1); > } > > sleep(-1); > } > > #define _GNU_SOURCE > #include <stdio.h> > #include <unistd.h> > #include <stdlib.h> > #include <sys/stat.h> > #include <sys/types.h> > #include <errno.h> > #include <sys/mount.h> > #include <sys/syscall.h> > #include <sched.h> > > int main() > { > const char *child = "/tmp/child"; > int ret; > > printf("main pid = %d\n", getpid()); > > /* make our own private playground ... */ > ret = unshare(CLONE_NEWNS); > if (ret) { > perror("unshare"); > exit(1); > } > > ret = mount("none", "/", NULL, MS_REC|MS_PRIVATE, NULL); > if (ret) { > perror("mount"); > exit(1); > } > > ret = mount("none", "/", NULL, MS_REC|MS_SHARED, NULL); > if (ret) { > perror("mount2"); > exit(1); > } > > /* fork monitor ... */ > ret = fork(); > if (ret < 0) { > perror("fork"); > exit(1); > } else if (!ret) { > printf("monitor pid = %d\n", getpid()); > > ret = unshare(CLONE_NEWNS); > if (ret) { > perror("unshare in monitor"); > exit(1); > } > > ret = mount("none", "/", NULL, MS_REC|MS_SHARED, NULL); > if (ret) { > perror("mount in monitor"); > exit(1); > } > > ret = mount("none", "/", NULL, MS_REC|MS_SLAVE, NULL); > if (ret) { > perror("mount2 in monitor"); > exit(1); > } > > sleep(-1); > } > > /* wait monitor to setup */ > sleep(1); > > > /* fork child ... */ > ret = fork(); > if (ret < 0) { > perror("fork"); > exit(1); > } else if (!ret) { > printf("child pid = %d\n", getpid()); > > ret = unshare(CLONE_NEWNS); > if (ret) { > perror("unshare in child"); > exit(1); > } > > if (!fork()) { /* grand-child */ > printf("grand-child pid = %d\n", getpid()); > ret = unshare(CLONE_NEWNS); > if (ret) { > perror("unshare in grand-child"); > exit(1); > } > > ret = mount("none", "/", NULL, MS_REC|MS_SHARED, NULL); > if (ret) { > perror("mount in grand-child"); > exit(1); > } > > ret = mount("none", "/", NULL, MS_REC|MS_SLAVE, NULL); > if (ret) { > perror("mount2 in grand-child"); > exit(1); > } > > sleep(-1); > } > > sleep(-1); > } > > /* wait child and grand-child to setup */ > sleep(1); > > ret = mkdir(child, 0755); > if (ret && errno != EEXIST) { > perror("mkdir"); > exit(1); > } > > /* let "child" mount slip to everyone' namespaces ... */ > ret = mount(child, child, NULL, MS_BIND, NULL); > if (ret) { > perror("bind mount"); > exit(1); > } > > sleep(-1); > } > > _______________________________________________ > Devel mailing list > Devel@openvz.org > https://lists.openvz.org/mailman/listinfo/devel ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Devel] [PATCH] fs/pnode.c: treat zero mnt_group_id-s as unequal 2016-02-16 19:45 [PATCH] fs/pnode.c: treat zero mnt_group_id-s as unequal Maxim Patlasov 2016-02-16 19:54 ` Al Viro @ 2016-02-16 22:58 ` Andrew Vagin 1 sibling, 0 replies; 5+ messages in thread From: Andrew Vagin @ 2016-02-16 22:58 UTC (permalink / raw) To: Maxim Patlasov; +Cc: viro, linux-fsdevel, linux-kernel, devel On Tue, Feb 16, 2016 at 11:45:33AM -0800, Maxim Patlasov wrote: > propagate_one(m) calculates "type" argument for copy_tree() like this: > > > if (m->mnt_group_id == last_dest->mnt_group_id) { > > type = CL_MAKE_SHARED; > > } else { > > type = CL_SLAVE; > > if (IS_MNT_SHARED(m)) > > type |= CL_MAKE_SHARED; > > } > > The "type" argument then governs clone_mnt() behavior with respect to flags > and mnt_master of new mount. When we iterate through a slave group, it is > possible that both current "m" and "last_dest" are not shared (although, > both are slaves, i.e. have non-NULL mnt_master-s). Then the comparison > above erroneously makes new mount shared and sets its mnt_master to > last_source->mnt_master. The patch fixes the problem by handling zero > mnt_group_id-s as though they are unequal. > > The similar problem exists in the implementation of "else" clause above > when we have to ascend upward in the master/slave tree by calling: > > > last_source = last_source->mnt_master; > > last_dest = last_source->mnt_parent; > > proper number of times. The last step is governed by > "n->mnt_group_id != last_dest->mnt_group_id" condition that may lie if > both are zero. The patch fixes this case in the same way as the former one. > Acked-by: Andrei Vagin <avagin@virtuozzo.com> > Signed-off-by: Maxim Patlasov <mpatlasov@virtuozzo.com> > --- > fs/pnode.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/fs/pnode.c b/fs/pnode.c > index 6367e1e..abf156a 100644 > --- a/fs/pnode.c > +++ b/fs/pnode.c > @@ -212,7 +212,7 @@ static int propagate_one(struct mount *m) > /* skip if mountpoint isn't covered by it */ > if (!is_subdir(mp->m_dentry, m->mnt.mnt_root)) > return 0; > - if (m->mnt_group_id == last_dest->mnt_group_id) { > + if (m->mnt_group_id && m->mnt_group_id == last_dest->mnt_group_id) { > type = CL_MAKE_SHARED; > } else { > struct mount *n, *p; > @@ -223,7 +223,9 @@ static int propagate_one(struct mount *m) > last_source = last_source->mnt_master; > last_dest = last_source->mnt_parent; > } > - if (n->mnt_group_id != last_dest->mnt_group_id) { > + if (n->mnt_group_id != last_dest->mnt_group_id || > + (!n->mnt_group_id && > + !last_dest->mnt_group_id)) { > last_source = last_source->mnt_master; > last_dest = last_source->mnt_parent; > } > > _______________________________________________ > Devel mailing list > Devel@openvz.org > https://lists.openvz.org/mailman/listinfo/devel ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2016-02-26 0:26 UTC | newest] Thread overview: 5+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2016-02-16 19:45 [PATCH] fs/pnode.c: treat zero mnt_group_id-s as unequal Maxim Patlasov 2016-02-16 19:54 ` Al Viro 2016-02-17 7:07 ` Maxim Patlasov 2016-02-26 0:26 ` [Devel] " Andrew Vagin 2016-02-16 22:58 ` Andrew Vagin
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).