| Message ID | 20211201193750.2097885-5-catalin.marinas@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/4] mm: Introduce a 'min_size' argument to fault_in_*() | expand |
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index c7d74c8776a1..439cf38f320a 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2222,8 +2222,13 @@ static noinline int search_ioctl(struct inode *inode, key.offset = sk->min_offset; while (1) { + size_t len = *buf_size - sk_offset; ret = -EFAULT; - if (fault_in_writeable(ubuf + sk_offset, *buf_size - sk_offset, 0)) + /* + * Ensure that the whole user buffer is faulted in at sub-page + * granularity, otherwise the loop may live-lock. + */ + if (fault_in_writeable(ubuf + sk_offset, len, len)) break; ret = btrfs_search_forward(root, &key, path, sk->min_transid);
Commit a48b73eca4ce ("btrfs: fix potential deadlock in the search ioctl") addressed a lockdep warning by pre-faulting the user pages and attempting the copy_to_user_nofault() in an infinite loop. On architectures like arm64 with MTE, an access may fault within a page at a location different from what fault_in_writeable() probed. Since the sk_offset is rewound to the previous struct btrfs_ioctl_search_header boundary, there is no guaranteed forward progress and search_ioctl() may live-lock. Request a 'min_size' of (*buf_size - sk_offset) from fault_in_writeable() to check this range for sub-page faults. Fixes: a48b73eca4ce ("btrfs: fix potential deadlock in the search ioctl") Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Reported-by: Al Viro <viro@zeniv.linux.org.uk> --- fs/btrfs/ioctl.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)