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| author | Andrew Elble <aweits@rit.edu> | 2015-02-23 08:51:24 -0500 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2015-04-11 22:24:34 -0400 |
| commit | c1b8940b42bb6487b10f2267a96b486276ce9ff7 (patch) | |
| tree | 05d3eca8e97ba0459e18eb32fe7f2e76c0d38789 /fs/open.c | |
| parent | 3d330dc175d3faf518cf035be5ae6a39bf256e6e (diff) | |
| download | lwn-c1b8940b42bb6487b10f2267a96b486276ce9ff7.tar.gz lwn-c1b8940b42bb6487b10f2267a96b486276ce9ff7.zip | |
NFS: fix BUG() crash in notify_change() with patch to chown_common()
We have observed a BUG() crash in fs/attr.c:notify_change(). The crash
occurs during an rsync into a filesystem that is exported via NFS.
1.) fs/attr.c:notify_change() modifies the caller's version of attr.
2.) 6de0ec00ba8d ("VFS: make notify_change pass ATTR_KILL_S*ID to
setattr operations") introduced a BUG() restriction such that "no
function will ever call notify_change() with both ATTR_MODE and
ATTR_KILL_S*ID set". Under some circumstances though, it will have
assisted in setting the caller's version of attr to this very
combination.
3.) 27ac0ffeac80 ("locks: break delegations on any attribute
modification") introduced code to handle breaking
delegations. This can result in notify_change() being re-called. attr
_must_ be explicitly reset to avoid triggering the BUG() established
in #2.
4.) The path that that triggers this is via fs/open.c:chmod_common().
The combination of attr flags set here and in the first call to
notify_change() along with a later failed break_deleg_wait()
results in notify_change() being called again via retry_deleg
without resetting attr.
Solution is to move retry_deleg in chmod_common() a bit further up to
ensure attr is completely reset.
There are other places where this seemingly could occur, such as
fs/utimes.c:utimes_common(), but the attr flags are not initially
set in such a way to trigger this.
Fixes: 27ac0ffeac80 ("locks: break delegations on any attribute modification")
Reported-by: Eric Meddaugh <etmsys@rit.edu>
Tested-by: Eric Meddaugh <etmsys@rit.edu>
Signed-off-by: Andrew Elble <aweits@rit.edu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/open.c')
| -rw-r--r-- | fs/open.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/open.c b/fs/open.c index ebcc7df0c9b6..6a83c47d5904 100644 --- a/fs/open.c +++ b/fs/open.c @@ -570,6 +570,7 @@ static int chown_common(struct path *path, uid_t user, gid_t group) uid = make_kuid(current_user_ns(), user); gid = make_kgid(current_user_ns(), group); +retry_deleg: newattrs.ia_valid = ATTR_CTIME; if (user != (uid_t) -1) { if (!uid_valid(uid)) @@ -586,7 +587,6 @@ static int chown_common(struct path *path, uid_t user, gid_t group) if (!S_ISDIR(inode->i_mode)) newattrs.ia_valid |= ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV; -retry_deleg: mutex_lock(&inode->i_mutex); error = security_path_chown(path, uid, gid); if (!error) |