dump_header() always requires tasklist_lock to be held because it calls
dump_tasks() which iterates through the tasklist. There are a few places
where this isn't maintained, so make sure tasklist_lock is always held
whenever calling dump_header().
This also fixes the pagefault case where oom_kill_process() is called on
current without tasklist_lock. It is necessary to hold a readlock for
both calling dump_header() and iterating its children.
Reported-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
mm/oom_kill.c | 23 ++++++++++-------------
1 files changed, 10 insertions(+), 13 deletions(-)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -395,6 +395,9 @@ static void dump_tasks(const struct mem_cgroup *mem)
} while_each_thread(g, p);
}
+/*
+ * Call with tasklist_lock read-locked.
+ */
static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
struct mem_cgroup *mem)
{
@@ -641,8 +644,8 @@ retry:
/* Found nothing?!?! Either we hang forever, or we panic. */
if (!p) {
- read_unlock(&tasklist_lock);
dump_header(NULL, gfp_mask, order, NULL);
+ read_unlock(&tasklist_lock);
panic("Out of memory and no killable processes...\n");
}
@@ -675,11 +678,6 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
/* Got some memory back in the last second. */
return;
- if (sysctl_panic_on_oom == 2) {
- dump_header(NULL, gfp_mask, order, NULL);
- panic("out of memory. Compulsory panic_on_oom is selected.\n");
- }
-
/*
* Check if there were limitations on the allocation (only relevant for
* NUMA) that may require different handling.
@@ -688,15 +686,12 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
&totalpages);
read_lock(&tasklist_lock);
if (unlikely(sysctl_panic_on_oom)) {
- /*
- * panic_on_oom only affects CONSTRAINT_NONE, the kernel
- * should not panic for cpuset or mempolicy induced memory
- * failures.
- */
- if (constraint == CONSTRAINT_NONE) {
+ if (sysctl_panic_on_oom == 2 || constraint == CONSTRAINT_NONE) {
dump_header(NULL, gfp_mask, order, NULL);
read_unlock(&tasklist_lock);
- panic("Out of memory: panic_on_oom is enabled\n");
+ panic("Out of memory: %s panic_on_oom is enabled\n",
+ sysctl_panic_on_oom == 2 ? "compulsory" :
+ "system-wide");
}
}
__out_of_memory(gfp_mask, order, totalpages, constraint, nodemask);
@@ -724,8 +719,10 @@ void pagefault_out_of_memory(void)
if (try_set_system_oom()) {
constrained_alloc(NULL, 0, NULL, &totalpages);
+ read_lock(&tasklist_lock);
err = oom_kill_process(current, 0, 0, 0, totalpages, NULL,
"Out of memory (pagefault)");
+ read_unlock(&tasklist_lock);
if (err)
out_of_memory(NULL, 0, 0, NULL);
clear_system_oom();
--
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