free_ret_instance() has two unrelated responsibilities: actually cleaning up return_instance's resources and freeing memory, and also helping with utask->return_instances list traversal by returning the next alive pointer. There is no reason why these two aspects have to be mixed together, so turn free_ret_instance() into void-returning function and make callers do list traversal on their own. We'll use this simplification in the next patch that will guarantee that to-be-freed return_instance isn't reachable from utask->return_instances list. Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx> --- kernel/events/uprobes.c | 37 +++++++++++++++++++++---------------- 1 file changed, 21 insertions(+), 16 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 6beac52239be..cca1fe4a3fb1 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -1888,10 +1888,8 @@ unsigned long uprobe_get_trap_addr(struct pt_regs *regs) return instruction_pointer(regs); } -static struct return_instance *free_ret_instance(struct return_instance *ri, bool cleanup_hprobe) +static void free_ret_instance(struct return_instance *ri, bool cleanup_hprobe) { - struct return_instance *next = ri->next; - if (cleanup_hprobe) { enum hprobe_state hstate; @@ -1901,7 +1899,6 @@ static struct return_instance *free_ret_instance(struct return_instance *ri, boo kfree(ri->extra_consumers); kfree_rcu(ri, rcu); - return next; } /* @@ -1911,7 +1908,7 @@ static struct return_instance *free_ret_instance(struct return_instance *ri, boo void uprobe_free_utask(struct task_struct *t) { struct uprobe_task *utask = t->utask; - struct return_instance *ri; + struct return_instance *ri, *ri_next; if (!utask) return; @@ -1921,8 +1918,11 @@ void uprobe_free_utask(struct task_struct *t) timer_delete_sync(&utask->ri_timer); ri = utask->return_instances; - while (ri) - ri = free_ret_instance(ri, true /* cleanup_hprobe */); + while (ri) { + ri_next = ri->next; + free_ret_instance(ri, true /* cleanup_hprobe */); + ri = ri_next; + } kfree(utask); t->utask = NULL; @@ -2111,12 +2111,15 @@ unsigned long uprobe_get_trampoline_vaddr(void) static void cleanup_return_instances(struct uprobe_task *utask, bool chained, struct pt_regs *regs) { - struct return_instance *ri = utask->return_instances; + struct return_instance *ri = utask->return_instances, *ri_next; enum rp_check ctx = chained ? RP_CHECK_CHAIN_CALL : RP_CHECK_CALL; while (ri && !arch_uretprobe_is_alive(ri, ctx, regs)) { - ri = free_ret_instance(ri, true /* cleanup_hprobe */); + ri_next = ri->next; utask->depth--; + + free_ret_instance(ri, true /* cleanup_hprobe */); + ri = ri_next; } rcu_assign_pointer(utask->return_instances, ri); } @@ -2508,7 +2511,7 @@ static struct return_instance *find_next_ret_chain(struct return_instance *ri) void uprobe_handle_trampoline(struct pt_regs *regs) { struct uprobe_task *utask; - struct return_instance *ri, *next; + struct return_instance *ri, *ri_next, *next_chain; struct uprobe *uprobe; enum hprobe_state hstate; bool valid; @@ -2528,8 +2531,8 @@ void uprobe_handle_trampoline(struct pt_regs *regs) * or NULL; the latter case means that nobody but ri->func * could hit this trampoline on return. TODO: sigaltstack(). */ - next = find_next_ret_chain(ri); - valid = !next || arch_uretprobe_is_alive(next, RP_CHECK_RET, regs); + next_chain = find_next_ret_chain(ri); + valid = !next_chain || arch_uretprobe_is_alive(next_chain, RP_CHECK_RET, regs); instruction_pointer_set(regs, ri->orig_ret_vaddr); do { @@ -2541,7 +2544,9 @@ void uprobe_handle_trampoline(struct pt_regs *regs) * trampoline addresses on the stack are replaced with correct * original return addresses */ - rcu_assign_pointer(utask->return_instances, ri->next); + ri_next = ri->next; + rcu_assign_pointer(utask->return_instances, ri_next); + utask->depth--; uprobe = hprobe_consume(&ri->hprobe, &hstate); if (valid) @@ -2549,9 +2554,9 @@ void uprobe_handle_trampoline(struct pt_regs *regs) hprobe_finalize(&ri->hprobe, hstate); /* We already took care of hprobe, no need to waste more time on that. */ - ri = free_ret_instance(ri, false /* !cleanup_hprobe */); - utask->depth--; - } while (ri != next); + free_ret_instance(ri, false /* !cleanup_hprobe */); + ri = ri_next; + } while (ri != next_chain); } while (!valid); return; -- 2.43.5