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authorAndrew Elble <aweits@rit.edu>2015-02-23 08:51:24 -0500
committerAl Viro <viro@zeniv.linux.org.uk>2015-04-11 22:24:34 -0400
commitc1b8940b42bb6487b10f2267a96b486276ce9ff7 (patch)
tree05d3eca8e97ba0459e18eb32fe7f2e76c0d38789 /mm/shmem.c
parent3d330dc175d3faf518cf035be5ae6a39bf256e6e (diff)
downloadlinux-c1b8940b42bb6487b10f2267a96b486276ce9ff7.tar.bz2
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>
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