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authorLi Zefan <lizf@cn.fujitsu.com>2012-03-12 16:39:48 +0800
committerDavid Sterba <dsterba@suse.cz>2012-04-18 19:22:18 +0200
commitcdc6a3952558f00b1bc3b6401e1cf98797632fe2 (patch)
treeb97cf714429b439c6887b2fe0acf9065e1d09f1f /fs
parent8e52acf70459020d7e9e9fda25066be4da520943 (diff)
downloadlinux-linaro-stable-cdc6a3952558f00b1bc3b6401e1cf98797632fe2.tar.gz
Btrfs: avoid possible use-after-free in clear_extent_bit()
clear_extent_bit() { next_node = rb_next(&state->rb_node); ... clear_state_bit(state); <-- this may free next_node if (next_node) { state = rb_entry(next_node); ... } } clear_state_bit() calls merge_state() which may free the next node of the passing extent_state, so clear_extent_bit() may end up referencing freed memory. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/btrfs/extent_io.c36
1 files changed, 21 insertions, 15 deletions
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 05951bdf72cc..11eeb81fe695 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -402,6 +402,15 @@ static int split_state(struct extent_io_tree *tree, struct extent_state *orig,
return 0;
}
+static struct extent_state *next_state(struct extent_state *state)
+{
+ struct rb_node *next = rb_next(&state->rb_node);
+ if (next)
+ return rb_entry(next, struct extent_state, rb_node);
+ else
+ return NULL;
+}
+
/*
* utility function to clear some bits in an extent state struct.
* it will optionally wake up any one waiting on this state (wake == 1)
@@ -409,10 +418,11 @@ static int split_state(struct extent_io_tree *tree, struct extent_state *orig,
* If no bits are set on the state struct after clearing things, the
* struct is freed and removed from the tree
*/
-static void clear_state_bit(struct extent_io_tree *tree,
- struct extent_state *state,
- int *bits, int wake)
+static struct extent_state *clear_state_bit(struct extent_io_tree *tree,
+ struct extent_state *state,
+ int *bits, int wake)
{
+ struct extent_state *next;
int bits_to_clear = *bits & ~EXTENT_CTLBITS;
if ((bits_to_clear & EXTENT_DIRTY) && (state->state & EXTENT_DIRTY)) {
@@ -425,6 +435,7 @@ static void clear_state_bit(struct extent_io_tree *tree,
if (wake)
wake_up(&state->wq);
if (state->state == 0) {
+ next = next_state(state);
if (state->tree) {
rb_erase(&state->rb_node, &tree->state);
state->tree = NULL;
@@ -434,7 +445,9 @@ static void clear_state_bit(struct extent_io_tree *tree,
}
} else {
merge_state(tree, state);
+ next = next_state(state);
}
+ return next;
}
static struct extent_state *
@@ -473,7 +486,6 @@ int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
struct extent_state *state;
struct extent_state *cached;
struct extent_state *prealloc = NULL;
- struct rb_node *next_node;
struct rb_node *node;
u64 last_end;
int err;
@@ -525,14 +537,11 @@ hit_next:
WARN_ON(state->end < start);
last_end = state->end;
- if (state->end < end && !need_resched())
- next_node = rb_next(&state->rb_node);
- else
- next_node = NULL;
-
/* the state doesn't have the wanted bits, go ahead */
- if (!(state->state & bits))
+ if (!(state->state & bits)) {
+ state = next_state(state);
goto next;
+ }
/*
* | ---- desired range ---- |
@@ -590,16 +599,13 @@ hit_next:
goto out;
}
- clear_state_bit(tree, state, &bits, wake);
+ state = clear_state_bit(tree, state, &bits, wake);
next:
if (last_end == (u64)-1)
goto out;
start = last_end + 1;
- if (start <= end && next_node) {
- state = rb_entry(next_node, struct extent_state,
- rb_node);
+ if (start <= end && state && !need_resched())
goto hit_next;
- }
goto search_again;
out: