On Sat, Sep 05, 2009 at 12:25:37AM -0400, Nicolas Pitre wrote: > In ext2_rename(), dir_page is acquired through ext2_dotdot(). It is > then released through ext2_set_link() but only if old_dir != new_dir. > Failing that, the pkmap reference count is never decremented and the > page remains pinned forever. Repeat that a couple times with highmem > pages and all pkmap slots get exhausted, and every further kmap() calls > end up stalling on the pkmap_map_wait queue at which point the whole > system comes to a halt. > > Signed-off-by: Nicolas Pitre <nico@xxxxxxxxxxx> Acked-by: "Theodore Ts'o" <tytso@xxxxxxx> > I ran into this issue while testing highmem on ARM by running the git > test suite in a loop with 3 parallel instances. Using the right mv > sequence in a script would constitute a pretty simple recipe for a > local DoS on systems running ext2 and highmem. No idea if ext3 or ext4 > have the same issue. This is an ext2-only issue; for journalling reasons ext3 and ext4 read and write the directory via buffer heads. So this issue won't apply for ext3 or ext4. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
