diff options
| author | Brian Behlendorf <[email protected]> | 2011-11-01 13:07:41 -0700 |
|---|---|---|
| committer | Brian Behlendorf <[email protected]> | 2011-11-03 10:15:39 -0700 |
| commit | 6a95d0b74c2951f0dc82361ea279f64a7349f060 (patch) | |
| tree | 1401df8a79823003f52821d83ac274c5365864e9 | |
| parent | a7b125e9a577cbf66ddbd7cf9701028ff150ee8e (diff) | |
Fix NULL deref in balance_pgdat()
Be careful not to unconditionally clear the PF_MEMALLOC bit in
the task structure. It may have already been set when entering
zpl_putpage() in which case it must remain set on exit. In
particular the kswapd thread will have PF_MEMALLOC set in
order to prevent it from entering direct reclaim. By clearing
it we allow the following NULL deref to potentially occur.
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffff8109c7ab>] balance_pgdat+0x25b/0x4ff
Signed-off-by: Brian Behlendorf <[email protected]>
Issue #287
| -rw-r--r-- | module/zfs/zpl_file.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/module/zfs/zpl_file.c b/module/zfs/zpl_file.c index af46afddf..298c0b62d 100644 --- a/module/zfs/zpl_file.c +++ b/module/zfs/zpl_file.c @@ -324,9 +324,13 @@ zpl_putpage(struct page *pp, struct writeback_control *wbc, void *data) * the VM might try to write out additional pages by calling * zpl_putpage() again resulting in a deadlock. */ - current->flags |= PF_MEMALLOC; - (void) zfs_putpage(mapping->host, pp, wbc); - current->flags &= ~PF_MEMALLOC; + if (current->flags & PF_MEMALLOC) { + (void) zfs_putpage(mapping->host, pp, wbc); + } else { + current->flags |= PF_MEMALLOC; + (void) zfs_putpage(mapping->host, pp, wbc); + current->flags &= ~PF_MEMALLOC; + } return (0); } |