Messages in this thread Patch in this message |  | | | Subject | Re: 2.6.35-rc4 - include/linux/fdtable.h:85 invoked rcu_dereference_check() without protection! | | From | Eric Dumazet <> | | Date | Wed, 07 Jul 2010 06:37:28 +0200 |
| |
Le mercredi 07 juillet 2010 à 06:34 +0200, Eric Dumazet a écrit :
> Miles, you already posted this three times, and a fix is known. > > BTW, I dont know why it's not already in, Paul submitted it several > times, but nobody cares. > > http://kerneltrap.org/mailarchive/linux-kernel/2010/6/17/4584014 > > I am going to Ack it, maybe some other guys can help to. >
Ah, its in Andrew tree since 6 days, it should be sent to Linus promptly now...
The patch titled vfs: fix RCU-lockdep false positive due to /proc has been added to the -mm tree. Its filename is vfs-fix-rcu-lockdep-false-positive-due-to-proc.patch
Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------ Subject: vfs: fix RCU-lockdep false positive due to /proc From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> If a single-threaded process does a file-descriptor operation, and some other process accesses that same file descriptor via /proc, the current rcu_dereference_check_fdtable() can give a false-positive RCU-lockdep splat due to the reference count being increased by the /proc access after the reference-count check in fget_light() but before the check in rcu_dereference_check_fdtable().
This commit prevents this false positive by checking for a single-threaded process. To avoid #include hell, this commit uses the wrapper for thread_group_empty(current) defined by rcu_my_thread_group_empty() provided in a separate commit.
Located-by: Miles Lane <miles.lane@gmail.com> Located-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> --- include/linux/fdtable.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff -puN include/linux/fdtable.h~vfs-fix-rcu-lockdep-false-positive-due-to-proc include/linux/fdtable.h --- a/include/linux/fdtable.h~vfs-fix-rcu-lockdep-false-positive-due-to-proc +++ a/include/linux/fdtable.h @@ -62,7 +62,8 @@ struct files_struct { (rcu_dereference_check((fdtfd), \ rcu_read_lock_held() || \ lockdep_is_held(&(files)->file_lock) || \ - atomic_read(&(files)->count) == 1)) + atomic_read(&(files)->count) == 1 || \ + rcu_my_thread_group_empty())) #define files_fdtable(files) \ (rcu_dereference_check_fdtable((files), (files)->fdt)) _ Patches currently in -mm which might be from paulmck@linux.vnet.ibm.com are
origin.patch fs-fcntlc-kill_fasync_rcu-fa_lock-must-be-irq-safe.patch linux-next.patch vfs-fix-rcu-lockdep-false-positive-due-to-proc.patch vfs-use-kmalloc-to-allocate-fdmem-if-possible.patch
-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |