From: Dmitry Ilvokhin <d@ilvokhin.com>
To: Xiang Gao <gxxa03070307@gmail.com>
Cc: peterz@infradead.org, mingo@redhat.com, will@kernel.org,
boqun@kernel.org, longman@redhat.com,
linux-kernel@vger.kernel.org, Xiang Gao <gaoxiang17@xiaomi.com>
Subject: Re: [PATCH] lockdep: fix NULL pointer dereference in __lock_set_class()
Date: Thu, 16 Apr 2026 15:20:54 +0000 [thread overview]
Message-ID: <aeD-VmTjj5lpuGQX@shell.ilvokhin.com> (raw)
In-Reply-To: <20260416085443.927247-1-gxxa03070307@gmail.com>
On Thu, Apr 16, 2026 at 04:54:43PM +0800, Xiang Gao wrote:
> From: Xiang Gao <gaoxiang17@xiaomi.com>
>
> register_lock_class() can return NULL on failure (e.g., exceeding
> MAX_LOCKDEP_KEYS or lock_keys_in_use overflow). __lock_set_class()
> uses the return value directly in pointer arithmetic without a NULL
> check:
>
> class = register_lock_class(lock, subclass, 0);
> hlock->class_idx = class - lock_classes;
>
> If class is NULL, this computes a garbage negative offset that corrupts
> hlock->class_idx (a bitfield). Any subsequent hlock_class() call on
> this hlock returns a garbage pointer, leading to memory corruption or
> a crash.
>
> The other call site in __lock_acquire() (line 5112) already handles
> this correctly with an explicit NULL check. Add the same guard here.
>
> Signed-off-by: Xiang Gao <gaoxiang17@xiaomi.com>
Reviewed-by: Dmitry Ilvokhin <d@ilvokhin.com>
prev parent reply other threads:[~2026-04-16 15:20 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-16 8:54 [PATCH] lockdep: fix NULL pointer dereference in __lock_set_class() Xiang Gao
2026-04-16 15:04 ` Waiman Long
2026-04-16 15:20 ` Dmitry Ilvokhin [this message]
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