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authorPavel Emelyanov <xemul@openvz.org>2007-09-20 12:45:02 +0400
committerJ. Bruce Fields <bfields@citi.umich.edu>2007-10-09 18:32:45 -0400
commit85c59580b30c82aa771aa33b37217a6b6851bc14 (patch)
tree02e96b437a63908ad3791021d352ad2aefff9936 /Documentation/00-INDEX
parentf0c1cd0eaf0b127356c2c09e40305453bc361b0f (diff)
locks: Fix potential OOPS in generic_setlease()
This code is run under lock_kernel(), which is dropped during sleeping operations, so the following race is possible: CPU1: CPU2: vfs_setlease(); vfs_setlease(); lock_kernel(); lock_kernel(); /* spin */ generic_setlease(): ... for (before = ...) /* here we found some lease after * which we will insert the new one */ fl = locks_alloc_lock(); /* go to sleep in this allocation and * drop the BKL */ generic_setlease(): ... for (before = ...) /* here we find the "before" pointing * at the one we found on CPU1 */ ->fl_change(my_before, arg); lease_modify(); locks_free_lock(); /* and we freed it */ ... unlock_kernel(); locks_insert_lock(before, fl); /* OOPS! We have just tried to add the lease * at the tail of already removed one */ The similar races are already handled in other code - all the allocations are performed before any checks/updates. Thanks to Kamalesh Babulal for testing and for a bug report on an earlier version. Signed-off-by: Pavel Emelyanov <xemul@openvz.org> Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu> Cc: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
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