Messages in this thread Patch in this message | | | From | Catalin Marinas <> | Subject | [PATCH 3/3] btrfs: Avoid live-lock in search_ioctl() on hardware with sub-page faults | Date | Wed, 24 Nov 2021 19:20:24 +0000 |
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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_exact_writeable() instead which probes the entire user buffer for faults at sub-page granularity.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Reported-by: Al Viro <viro@zeniv.linux.org.uk> --- fs/btrfs/ioctl.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 92138ac2a4e2..23167c72fa47 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2223,7 +2223,8 @@ static noinline int search_ioctl(struct inode *inode, while (1) { ret = -EFAULT; - if (fault_in_writeable(ubuf + sk_offset, *buf_size - sk_offset)) + if (fault_in_exact_writeable(ubuf + sk_offset, + *buf_size - sk_offset)) break; ret = btrfs_search_forward(root, &key, path, sk->min_transid);
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