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From: David Sterba <dsterba@suse.cz>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Andreas Gruenbacher <agruenba@redhat.com>,
	Josef Bacik <josef@toxicpanda.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Andrew Morton <akpm@linux-foundation.org>,
	Chris Mason <clm@fb.com>, David Sterba <dsterba@suse.com>,
	Will Deacon <will@kernel.org>,
	linux-fsdevel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 3/3] btrfs: Avoid live-lock in search_ioctl() on hardware with sub-page faults
Date: Thu, 7 Apr 2022 13:05:18 +0200	[thread overview]
Message-ID: <20220407110518.GE15609@twin.jikos.cz> (raw)
In-Reply-To: <20220406180922.1522433-4-catalin.marinas@arm.com>

On Wed, Apr 06, 2022 at 07:09:22PM +0100, Catalin Marinas wrote:
> 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>

WARNING: multiple messages have this Message-ID (diff)
From: David Sterba <dsterba@suse.cz>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Andreas Gruenbacher <agruenba@redhat.com>,
	Josef Bacik <josef@toxicpanda.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Andrew Morton <akpm@linux-foundation.org>,
	Chris Mason <clm@fb.com>, David Sterba <dsterba@suse.com>,
	Will Deacon <will@kernel.org>,
	linux-fsdevel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 3/3] btrfs: Avoid live-lock in search_ioctl() on hardware with sub-page faults
Date: Thu, 7 Apr 2022 13:05:18 +0200	[thread overview]
Message-ID: <20220407110518.GE15609@twin.jikos.cz> (raw)
In-Reply-To: <20220406180922.1522433-4-catalin.marinas@arm.com>

On Wed, Apr 06, 2022 at 07:09:22PM +0100, Catalin Marinas wrote:
> 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>

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  parent reply	other threads:[~2022-04-07 11:09 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-06 18:09 [PATCH v3 0/3] Avoid live-lock in btrfs fault-in+uaccess loop Catalin Marinas
2022-04-06 18:09 ` Catalin Marinas
2022-04-06 18:09 ` [PATCH v3 1/3] mm: Add fault_in_subpage_writeable() to probe at sub-page granularity Catalin Marinas
2022-04-06 18:09   ` Catalin Marinas
2022-04-06 18:09 ` [PATCH v3 2/3] arm64: Add support for user sub-page fault probing Catalin Marinas
2022-04-06 18:09   ` Catalin Marinas
2022-04-06 18:09 ` [PATCH v3 3/3] btrfs: Avoid live-lock in search_ioctl() on hardware with sub-page faults Catalin Marinas
2022-04-06 18:09   ` Catalin Marinas
2022-04-06 20:40   ` Catalin Marinas
2022-04-06 20:40     ` Catalin Marinas
2022-04-07 11:05   ` David Sterba [this message]
2022-04-07 11:05     ` David Sterba

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