Commit dc0a241c authored by Michael Jeanson's avatar Michael Jeanson Committed by Ingo Molnar
Browse files

rseq: Fix rseq registration with CONFIG_DEBUG_RSEQ 



With CONFIG_DEBUG_RSEQ=y, at rseq registration the read-only fields are
copied from user-space, if this copy fails the syscall returns -EFAULT
and the registration should not be activated - but it erroneously is.

Move the activation of the registration after the copy of the fields to
fix this bug.

Fixes: 7d5265ff ("rseq: Validate read-only fields under DEBUG_RSEQ config")
Signed-off-by: default avatarMichael Jeanson <mjeanson@efficios.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/r/20250219205330.324770-1-mjeanson@efficios.com
parent 02d954c0

kernel/rseq.c

+8 −3
Original line number Diff line number Diff line
@@ -507,9 +507,6 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, 
		return -EINVAL;

	if (!access_ok(rseq, rseq_len))

		return -EFAULT;

	current->rseq = rseq;

	current->rseq_len = rseq_len;

	current->rseq_sig = sig;

#ifdef CONFIG_DEBUG_RSEQ

	/*

	 * Initialize the in-kernel rseq fields copy for validation of
@@ -521,6 +518,14 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, 
	    get_user(rseq_kernel_fields(current)->mm_cid, &rseq->mm_cid))

		return -EFAULT;

#endif

	/*

	 * Activate the registration by setting the rseq area address, length

	 * and signature in the task struct.

	 */

	current->rseq = rseq;

	current->rseq_len = rseq_len;

	current->rseq_sig = sig;



	/*

	 * If rseq was previously inactive, and has just been

	 * registered, ensure the cpu_id_start and cpu_id fields