Revision 68e23840d424b9ee403f09dcbdc106327d385ece authored by Konstantin Belousov on 23 January 2010, 19:01:25 UTC, committed by Konstantin Belousov on 23 January 2010, 19:01:25 UTC
The quotactl, statfs and fstatfs syscall implementations may dereference NULL pointer to struct mount if the looked up vnode is reclaimed. Also, these syscalls only mnt_ref() the mp, still allowing it to be unmounted; only struct mount memory is kept from being reused. Lock the vnode when doing name lookup, then reference its mount point, unlock the vnode and vfs_busy the mountpoint. This sequence shall take care of both races. MFC r188141 (by trasz): In some situations, mnt_lockref could go negative due to vfs_unbusy() being called without calling vfs_busy() first. This made umount(8) hang waiting for mnt_lockref to become zero, which would never happen. MFC r196887: In fhopen, vfs_ref() the mount point while vnode is unlocked, to prevent vn_start_write(NULL, &mp) from operating on potentially freed or reused struct mount *. Remove unmatched vfs_rel() in cleanup. Approved by: re (bz)
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