6.17-stable review patch. If anyone has any objections, please let me know.
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From: Saket Kumar Bhaskar skb99@linux.ibm.com
commit 7b6216baae751369195fa3c83d434d23bcda406a upstream.
A crash was observed when the sched_ext selftests runner was terminated with Ctrl+\ while test 15 was running:
NIP [c00000000028fa58] scx_enable.constprop.0+0x358/0x12b0 LR [c00000000028fa2c] scx_enable.constprop.0+0x32c/0x12b0 Call Trace: scx_enable.constprop.0+0x32c/0x12b0 (unreliable) bpf_struct_ops_link_create+0x18c/0x22c __sys_bpf+0x23f8/0x3044 sys_bpf+0x2c/0x6c system_call_exception+0x124/0x320 system_call_vectored_common+0x15c/0x2ec
kthread_run_worker() returns an ERR_PTR() on failure rather than NULL, but the current code in scx_alloc_and_add_sched() only checks for a NULL helper. Incase of failure on SIGQUIT, the error is not handled in scx_alloc_and_add_sched() and scx_enable() ends up dereferencing an error pointer.
Error handling is fixed in scx_alloc_and_add_sched() to propagate PTR_ERR() into ret, so that scx_enable() jumps to the existing error path, avoiding random dereference on failure.
Fixes: bff3b5aec1b7 ("sched_ext: Move disable machinery into scx_sched") Cc: stable@vger.kernel.org # v6.16+ Reported-and-tested-by: Samir Mulani samir@linux.ibm.com Signed-off-by: Saket Kumar Bhaskar skb99@linux.ibm.com Reviewed-by: Emil Tsalapatis emil@etsalapatis.com Reviewed-by: Andrea Righi arighi@nvidia.com Reviewed-by: Vishal Chourasia vishalc@linux.ibm.com Signed-off-by: Tejun Heo tj@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/sched/ext.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -4446,8 +4446,11 @@ static struct scx_sched *scx_alloc_and_a goto err_free_gdsqs;
sch->helper = kthread_run_worker(0, "sched_ext_helper"); - if (!sch->helper) + if (IS_ERR(sch->helper)) { + ret = PTR_ERR(sch->helper); goto err_free_pcpu; + } + sched_set_fifo(sch->helper->task);
atomic_set(&sch->exit_kind, SCX_EXIT_NONE);