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mm/vmalloc: do not warn on -ENOMEM from va_clip() in pcpu_get_vm_areas()

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When pcpu_get_vm_areas() has to split a free vmap_area in the middle
(NE_FIT_TYPE), va_clip() needs an extra vmap_area object. It takes the
per-cpu ne_fit_preload_node if one is there, and otherwise falls back
to kmem_cache_alloc(GFP_NOWAIT), which may fail and return -ENOMEM.
pcpu_get_vm_areas() never preloads, and a single call can do more than
one such split: on a NUMA system it places one area per node group, so
the first split consumes the preloaded object and the next one depends
on the GFP_NOWAIT allocation.

That failure is expected and already handled: the recovery path returns
the areas clipped so far to the free tree, purges lazily freed areas and
retries. But the error is checked with WARN_ON_ONCE(), so a transient
allocation failure under memory pressure or fault injection triggers a
kernel warning, and a panic with panic_on_warn. syzbot hit this on a
two-node VM while creating a per-cpu BPF array map.

Keep the WARN_ON_ONCE() for errors other than -ENOMEM, which do indicate
a bug, and take the recovery path either way. This matches what commit
b9183788a2 ("mm/vmalloc: do not warn on -ENOMEM from va_alloc()") did
for the other va_clip() caller.

Link: https://lore.kernel.org/20260925205450.21262-1-raghunathpalla.0209@gmail.com
Fixes: 1b23ff80b3 ("mm/vmalloc: invoke classify_va_fit_type() in adjust_va_to_fit_type()")
Signed-off-by: Palla Raghunath <raghunathpalla.0209@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: <syzbot+442828bb356b10813a47@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=442828bb356b10813a47
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Brigham Campbell <me@brighamcampbell.com>
Cc: Baoquan He <baoquan.he@linux.dev>
This commit is contained in:
Palla Raghunath 2026-09-25 21:54:49 +01:00 committed by Andrew Morton
parent 2e83e2ce34
commit 499baaff38
1 changed files with 7 additions and 2 deletions
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9
mm/vmalloc.c
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@ -5122,9 +5122,14 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
ret = va_clip(&free_vmap_area_root,
&free_vmap_area_list, va, start, size);
if (WARN_ON_ONCE(unlikely(ret)))
/* It is a BUG(), but trigger recovery instead. */
if (unlikely(ret)) {
/*
* -ENOMEM from the GFP_NOWAIT fallback is expected.
* Anything else is a BUG(), but trigger recovery instead.
*/
WARN_ON_ONCE(ret != -ENOMEM);
goto recovery;
}
/* Allocated area. */
va = vas[area];