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| author | Catalin Marinas <catalin.marinas@arm.com> | 2022-04-23 13:07:51 +0300 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2022-04-25 12:25:43 +0300 |
| commit | 18788e34642e2e3eae785b0966769d03e7fbe9d2 (patch) | |
| tree | 193b014c65f148ff90d755a838b848b29a6bdf39 /fs/btrfs/ioctl.c | |
| parent | f3ba50a7a100e91b0b13ca43190a66c1bfdb9993 (diff) | |
| download | linux-18788e34642e2e3eae785b0966769d03e7fbe9d2.tar.xz | |
btrfs: Avoid live-lock in search_ioctl() on hardware with sub-page faults
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.
Use fault_in_subpage_writeable() instead of fault_in_writeable() to
ensure the permission is checked at the right granularity (smaller than
PAGE_SIZE).
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Fixes: a48b73eca4ce ("btrfs: fix potential deadlock in the search ioctl")
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: David Sterba <dsterba@suse.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20220423100751.1870771-4-catalin.marinas@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'fs/btrfs/ioctl.c')
| -rw-r--r-- | fs/btrfs/ioctl.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index be6c24577dbe..9bf0616a3069 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2565,7 +2565,12 @@ static noinline int search_ioctl(struct inode *inode, while (1) { ret = -EFAULT; - if (fault_in_writeable(ubuf + sk_offset, *buf_size - sk_offset)) + /* + * Ensure that the whole user buffer is faulted in at sub-page + * granularity, otherwise the loop may live-lock. + */ + if (fault_in_subpage_writeable(ubuf + sk_offset, + *buf_size - sk_offset)) break; ret = btrfs_search_forward(root, &key, path, sk->min_transid); |