diff options
| author | Brian Behlendorf <[email protected]> | 2011-11-01 13:35:12 -0700 |
|---|---|---|
| committer | Brian Behlendorf <[email protected]> | 2011-11-03 09:50:22 -0700 |
| commit | b8b6e4c453929596b630fa1cca1ee26a532a2ab4 (patch) | |
| tree | 8da18ee0bd93b259a3f0366826f2ee11962adaf9 | |
| parent | 16952a68f25d55da21578f562b3813559fd01c6b (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
kv_alloc() 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]>
Closes ZFS issue #287
| -rw-r--r-- | module/spl/spl-kmem.c | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/module/spl/spl-kmem.c b/module/spl/spl-kmem.c index db009614f..b3c054a95 100644 --- a/module/spl/spl-kmem.c +++ b/module/spl/spl-kmem.c @@ -855,14 +855,17 @@ kv_alloc(spl_kmem_cache_t *skc, int size, int flags) * been filed at kernel.org to track the issue. * * https://bugzilla.kernel.org/show_bug.cgi?id=30702 + * + * NOTE: Only set PF_MEMALLOC if it's not already set, and + * then only clear it when we were the one who set it. */ - if (!(flags & __GFP_FS)) + if (!(flags & __GFP_FS) && !(current->flags & PF_MEMALLOC)) { current->flags |= PF_MEMALLOC; - - ptr = __vmalloc(size, flags | __GFP_HIGHMEM, PAGE_KERNEL); - - if (!(flags & __GFP_FS)) + ptr = __vmalloc(size, flags|__GFP_HIGHMEM, PAGE_KERNEL); current->flags &= ~PF_MEMALLOC; + } else { + ptr = __vmalloc(size, flags|__GFP_HIGHMEM, PAGE_KERNEL); + } } /* Resulting allocated memory will be page aligned */ |