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H A D | ioctl.c | 18788e34 Sat Apr 23 05:07:51 CDT 2022 Catalin Marinas <catalin.marinas@arm.com> 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>
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