diff options
authorDan Rosenberg <>2011-02-14 16:04:23 -0500
committerChris Mason <>2011-02-14 16:04:23 -0500
commit51788b1bdd0d68345bab0af4301e7fa429277228 (patch)
parent6848ad6461e551849ba3c32d945d4f45e96453a6 (diff)
btrfs: prevent heap corruption in btrfs_ioctl_space_info()
Commit bf5fc093c5b625e4259203f1cee7ca73488a5620 refactored btrfs_ioctl_space_info() and introduced several security issues. space_args.space_slots is an unsigned 64-bit type controlled by a possibly unprivileged caller. The comparison as a signed int type allows providing values that are treated as negative and cause the subsequent allocation size calculation to wrap, or be truncated to 0. By providing a size that's truncated to 0, kmalloc() will return ZERO_SIZE_PTR. It's also possible to provide a value smaller than the slot count. The subsequent loop ignores the allocation size when copying data in, resulting in a heap overflow or write to ZERO_SIZE_PTR. The fix changes the slot count type and comparison typecast to u64, which prevents truncation or signedness errors, and also ensures that we don't copy more data than we've allocated in the subsequent loop. Note that zero-size allocations are no longer possible since there is already an explicit check for space_args.space_slots being 0 and truncation of this value is no longer an issue. Signed-off-by: Dan Rosenberg <> Signed-off-by: Josef Bacik <> Reviewed-by: Josef Bacik <> Signed-off-by: Chris Mason <>
1 files changed, 8 insertions, 2 deletions
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 02d224e8c83f..be2d4f6aaa5e 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2208,7 +2208,7 @@ long btrfs_ioctl_space_info(struct btrfs_root *root, void __user *arg)
int num_types = 4;
int alloc_size;
int ret = 0;
- int slot_count = 0;
+ u64 slot_count = 0;
int i, c;
if (copy_from_user(&space_args,
@@ -2247,7 +2247,7 @@ long btrfs_ioctl_space_info(struct btrfs_root *root, void __user *arg)
goto out;
- slot_count = min_t(int, space_args.space_slots, slot_count);
+ slot_count = min_t(u64, space_args.space_slots, slot_count);
alloc_size = sizeof(*dest) * slot_count;
@@ -2267,6 +2267,9 @@ long btrfs_ioctl_space_info(struct btrfs_root *root, void __user *arg)
for (i = 0; i < num_types; i++) {
struct btrfs_space_info *tmp;
+ if (!slot_count)
+ break;
info = NULL;
list_for_each_entry_rcu(tmp, &root->fs_info->space_info,
@@ -2288,7 +2291,10 @@ long btrfs_ioctl_space_info(struct btrfs_root *root, void __user *arg)
memcpy(dest, &space, sizeof(space));
+ slot_count--;
+ if (!slot_count)
+ break;