| From: Catalin Marinas <catalin.marinas@arm.com> |
| Subject: 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_exact_writeable() instead which probes the entire user |
| buffer for faults at sub-page granularity. |
| |
| Link: https://lkml.kernel.org/r/20211124192024.2408218-4-catalin.marinas@arm.com |
| 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> |
| Acked-by: David Sterba <dsterba@suse.com> |
| Cc: Josef Bacik <josef@toxicpanda.com> |
| Cc: Andreas Gruenbacher <agruenba@redhat.com> |
| Cc: Will Deacon <will@kernel.org> |
| Cc: Matthew Wilcox <willy@infradead.org> |
| Cc: <stable@vger.kernel.org> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| --- |
| |
| fs/btrfs/ioctl.c | 3 ++- |
| 1 file changed, 2 insertions(+), 1 deletion(-) |
| |
| --- a/fs/btrfs/ioctl.c~btrfs-avoid-live-lock-in-search_ioctl-on-hardware-with-sub-page-faults |
| +++ a/fs/btrfs/ioctl.c |
| @@ -2225,7 +2225,8 @@ static noinline int search_ioctl(struct |
| |
| 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); |
| _ |
