4.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Sterba <dsterba@xxxxxxxx> commit 9dcbeed4d7e11e1dcf5e55475de3754f0855d1c2 upstream. The calculation of range length in btrfs_sync_file leads to signed overflow. This was caught by PaX gcc SIZE_OVERFLOW plugin. https://forums.grsecurity.net/viewtopic.php?f=1&t=4284 The fsync call passes 0 and LLONG_MAX, the range length does not fit to loff_t and overflows, but the value is converted to u64 so it silently works as expected. The minimal fix is a typecast to u64, switching functions to take (start, end) instead of (start, len) would be more intrusive. Coccinelle script found that there's one more opencoded calculation of the length. <smpl> @@ loff_t start, end; @@ * end - start </smpl> Signed-off-by: David Sterba <dsterba@xxxxxxxx> Signed-off-by: Chris Mason <clm@xxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/btrfs/file.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1876,8 +1876,13 @@ int btrfs_sync_file(struct file *file, l struct btrfs_log_ctx ctx; int ret = 0; bool full_sync = 0; - const u64 len = end - start + 1; + u64 len; + /* + * The range length can be represented by u64, we have to do the typecasts + * to avoid signed overflow if it's [0, LLONG_MAX] eg. from fsync() + */ + len = (u64)end - (u64)start + 1; trace_btrfs_sync_file(file, datasync); /* @@ -2065,8 +2070,7 @@ int btrfs_sync_file(struct file *file, l } } if (!full_sync) { - ret = btrfs_wait_ordered_range(inode, start, - end - start + 1); + ret = btrfs_wait_ordered_range(inode, start, len); if (ret) { btrfs_end_transaction(trans, root); goto out; -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html