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| author | Al Viro <viro@zeniv.linux.org.uk> | 2010-08-09 18:05:43 +0200 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2010-08-09 22:49:01 +0200 |
| commit | 7a4dec53897ecd3367efb1e12fe8a4edc47dc0e9 (patch) | |
| tree | 31d4639522e1453a7f5c38aa2436ffdd6df5c60b /fs/namespace.c | |
| parent | vfs: don't hold s_umount over close_bdev_exclusive() call (diff) | |
| download | linux-7a4dec53897ecd3367efb1e12fe8a4edc47dc0e9.tar.xz linux-7a4dec53897ecd3367efb1e12fe8a4edc47dc0e9.zip | |
Fix sget() race with failing mount
If sget() finds a matching superblock being set up, it'll
grab an active reference to it and grab s_umount. That's
fine - we'll wait for completion of foofs_get_sb() that way.
However, if said foofs_get_sb() fails we'll end up holding
the halfway-created superblock. deactivate_locked_super()
called by foofs_get_sb() will just unlock the sucker since
we are holding another active reference to it.
What we need is a way to tell if superblock has been successfully
set up. Unfortunately, neither ->s_root nor the check for
MS_ACTIVE quite fit. Cheap and easy way, suitable for backport:
new flag set by the (only) caller of ->get_sb(). If that flag
isn't present by the time sget() grabbed s_umount on preexisting
superblock it has found, it's seeing a stillborn and should
just bury it with deactivate_locked_super() (and repeat the search).
Longer term we want to set that flag in ->get_sb() instances (and
check for it to distinguish between "sget() found us a live sb"
and "sget() has allocated an sb, we need to set it up" in there,
instead of checking ->s_root as we do now).
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@kernel.org
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index 88058de59c7c..32dcd24bbc9a 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1984,7 +1984,7 @@ long do_mount(char *dev_name, char *dir_name, char *type_page, if (flags & MS_RDONLY) mnt_flags |= MNT_READONLY; - flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | + flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | MS_STRICTATIME); |