The patch titled
r/o bind mounts: elevate write count open()'d files
has been removed from the -mm tree. Its filename was
r-o-bind-mounts-elevate-write-count-opend-files.patch
This patch was dropped because an updated version will be merged
------------------------------------------------------
Subject: r/o bind mounts: elevate write count open()'d files
From: Dave Hansen <haveblue@xxxxxxxxxx>
This is the first really tricky patch in the series. It elevates the writer
count on a mount each time a non-special file is opened for write.
This is not completely apparent in the patch because the two if() conditions
in may_open() above the mnt_want_write() call are, combined, equivalent to
special_file().
There is also an elevated count around the vfs_create() call in open_namei().
The count needs to be kept elevated all the way into the may_open() call.
Otherwise, when the write is dropped, a ro->rw transisition could occur. This
would lead to having rw access on the newly created file, while the vfsmount
is ro. That is bad.
Some filesystems forego the use of normal vfs calls to create struct files.
Make sure that these users elevate the mnt writer count because they will get
__fput(), and we need to make sure they're balanced.
Signed-off-by: Dave Hansen <haveblue@xxxxxxxxxx>
Acked-by: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/file_table.c | 9 ++++++++-
fs/namei.c | 20 ++++++++++++++++----
ipc/mqueue.c | 3 +++
3 files changed, 27 insertions(+), 5 deletions(-)
diff -puN fs/file_table.c~r-o-bind-mounts-elevate-write-count-opend-files fs/file_table.c
--- a/fs/file_table.c~r-o-bind-mounts-elevate-write-count-opend-files
+++ a/fs/file_table.c
@@ -193,6 +193,10 @@ int init_file(struct file *file, struct
file->f_mapping = dentry->d_inode->i_mapping;
file->f_mode = mode;
file->f_op = fop;
+ if (mode & FMODE_WRITE) {
+ error = mnt_want_write(mnt);
+ WARN_ON(error);
+ }
return error;
}
EXPORT_SYMBOL(init_file);
@@ -230,8 +234,11 @@ void fastcall __fput(struct file *file)
if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL))
cdev_put(inode->i_cdev);
fops_put(file->f_op);
- if (file->f_mode & FMODE_WRITE)
+ if (file->f_mode & FMODE_WRITE) {
put_write_access(inode);
+ if (!special_file(inode->i_mode))
+ mnt_drop_write(mnt);
+ }
put_pid(file->f_owner.pid);
file_kill(file);
file->f_path.dentry = NULL;
diff -puN fs/namei.c~r-o-bind-mounts-elevate-write-count-opend-files fs/namei.c
--- a/fs/namei.c~r-o-bind-mounts-elevate-write-count-opend-files
+++ a/fs/namei.c
@@ -1621,8 +1621,15 @@ int may_open(struct nameidata *nd, int a
return -EACCES;
flag &= ~O_TRUNC;
- } else if (IS_RDONLY(inode) && (flag & FMODE_WRITE))
- return -EROFS;
+ } else if (flag & FMODE_WRITE) {
+ /*
+ * effectively: !special_file()
+ * balanced by __fput()
+ */
+ error = mnt_want_write(nd->mnt);
+ if (error)
+ return error;
+ }
error = vfs_permission(nd, acc_mode);
if (error)
@@ -1767,14 +1774,17 @@ do_last:
}
if (IS_ERR(nd->intent.open.file)) {
- mutex_unlock(&dir->d_inode->i_mutex);
error = PTR_ERR(nd->intent.open.file);
- goto exit_dput;
+ goto exit_mutex_unlock;
}
/* Negative dentry, just create the file */
if (!path.dentry->d_inode) {
+ error = mnt_want_write(nd->mnt);
+ if (error)
+ goto exit_mutex_unlock;
error = open_namei_create(nd, &path, flag, mode);
+ mnt_drop_write(nd->mnt);
if (error)
goto exit;
return 0;
@@ -1812,6 +1822,8 @@ ok:
goto exit;
return 0;
+exit_mutex_unlock:
+ mutex_unlock(&dir->d_inode->i_mutex);
exit_dput:
dput_path(&path, nd);
exit:
diff -puN ipc/mqueue.c~r-o-bind-mounts-elevate-write-count-opend-files ipc/mqueue.c
--- a/ipc/mqueue.c~r-o-bind-mounts-elevate-write-count-opend-files
+++ a/ipc/mqueue.c
@@ -682,6 +682,9 @@ asmlinkage long sys_mq_open(const char _
goto out;
filp = do_open(dentry, oflag);
} else {
+ error = mnt_want_write(mqueue_mnt);
+ if (error)
+ goto out;
filp = do_create(mqueue_mnt->mnt_root, dentry,
oflag, mode, u_attr);
}
_
Patches currently in -mm which might be from haveblue@xxxxxxxxxx are
markers-fix-warnings.patch
maps4-add-proportional-set-size-accounting-in-smaps.patch
maps4-rework-task_size-macros.patch
maps4-move-is_swap_pte.patch
maps4-introduce-a-generic-page-walker.patch
maps4-use-pagewalker-in-clear_refs-and-smaps.patch
maps4-simplify-interdependence-of-maps-and-smaps.patch
maps4-move-clear_refs-code-to-task_mmuc.patch
maps4-regroup-task_mmu-by-interface.patch
maps4-add-proc-pid-pagemap-interface.patch
maps4-add-proc-kpagecount-interface.patch
maps4-add-proc-kpageflags-interface.patch
maps4-make-page-monitoring-proc-file-optional.patch
maps4-make-page-monitoring-proc-file-optional-fix.patch
hugetlb-split-alloc_huge_page-into-private-and-shared-components.patch
hugetlb-split-alloc_huge_page-into-private-and-shared-components-checkpatch-fixes.patch
hugetlb-fix-quota-management-for-private-mappings.patch
hugetlb-debit-quota-in-alloc_huge_page.patch
hugetlb-allow-bulk-updating-in-hugetlb__quota.patch
hugetlb-enforce-quotas-during-reservation-for-shared-mappings.patch
add-remove_memory-for-ppc64-2.patch
enable-hotplug-memory-remove-for-ppc64.patch
add-arch-specific-walk_memory_remove-for-ppc64.patch
r-o-bind-mounts-elevate-write-count-opend-files.patch
r-o-bind-mounts-elevate-write-count-for-some-ioctls.patch
ext2-reservations-fix-for-r-o-bind-mounts-take-writer-count-v2.patch
r-o-bind-mounts-elevate-writer-count-for-chown-and-friends.patch
r-o-bind-mounts-make-access-use-mnt-check.patch
r-o-bind-mounts-elevate-mnt-writers-for-callers-of-vfs_mkdir.patch
r-o-bind-mounts-elevate-write-count-during-entire-ncp_ioctl.patch
r-o-bind-mounts-elevate-write-count-during-entire-ncp_ioctl-fix.patch
r-o-bind-mounts-elevate-write-count-for-link-and-symlink-calls.patch
r-o-bind-mounts-elevate-mount-count-for-extended-attributes.patch
r-o-bind-mounts-elevate-write-count-for-file_update_time.patch
r-o-bind-mounts-unix_find_other-elevate-write-count-for-touch_atime.patch
r-o-bind-mounts-unix_find_other-elevate-write-count-for-touch_atime-fix.patch
r-o-bind-mounts-elevate-write-count-over-calls-to-vfs_rename.patch
r-o-bind-mounts-nfs-check-mnt-instead-of-superblock-directly.patch
r-o-bind-mounts-elevate-writer-count-for-do_sys_truncate.patch
r-o-bind-mounts-elevate-write-count-for-do_utimes.patch
r-o-bind-mounts-elevate-write-count-for-do_utimes-touch-command-causes-oops.patch
r-o-bind-mounts-elevate-write-count-for-do_sys_utime-and-touch_atime.patch
r-o-bind-mounts-sys_mknodat-elevate-write-count-for-vfs_mknod-create.patch
r-o-bind-mounts-sys_mknodat-elevate-write-count-for-vfs_mknod-create-fix.patch
r-o-bind-mounts-elevate-mnt-writers-for-vfs_unlink-callers.patch
r-o-bind-mounts-do_rmdir-elevate-write-count.patch
r-o-bind-mounts-track-number-of-mount-writers.patch
r-o-bind-mounts-track-number-of-mount-writers-make-lockdep-happy-with-r-o-bind-mounts.patch
r-o-bind-mounts-track-number-of-mount-writers-fix.patch
r-o-bind-mounts-honor-r-w-changes-at-do_remount-time.patch
reiser4.patch
page-owner-tracking-leak-detector.patch
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