On 22.12.2021 22:48, Manfred Spraul wrote: > One codepath in find_alloc_undo() calls kvfree() while holding a spinlock. > Since vfree() can sleep this is a bug. > > Previously, the code path used kfree(), and kfree() is safe to be called > while holding a spinlock. > > Minghao proposed to fix this by updating find_alloc_undo(). > > Alternate proposal to fix this: Instead of changing find_alloc_undo(), > change kvfree() so that the same rules as for kfree() apply: > Having different rules for kfree() and kvfree() just asks for bugs. > > Disadvantage: Releasing vmalloc'ed memory will be delayed a bit. > > Reported-by: Zeal Robot <zealci@xxxxxxxxxx> > Reported-by: Minghao Chi <chi.minghao@xxxxxxxxxx> > Link: https://lore.kernel.org/all/20211222081026.484058-1-chi.minghao@xxxxxxxxxx/ > Fixes: fc37a3b8b438 ("[PATCH] ipc sem: use kvmalloc for sem_undo allocation") > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx> > --- > mm/util.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/util.c b/mm/util.c > index 741ba32a43ac..7f9181998835 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -610,12 +610,12 @@ EXPORT_SYMBOL(kvmalloc_node); > * It is slightly more efficient to use kfree() or vfree() if you are certain > * that you know which one to use. > * > - * Context: Either preemptible task context or not-NMI interrupt. > + * Context: Any context except NMI interrupt. > */ > void kvfree(const void *addr) > { > if (is_vmalloc_addr(addr)) > - vfree(addr); > + vfree_atomic(addr); > else > kfree(addr); > } I would prefer to release memory ASAP if it's possible. What do you think about this change? --- a/mm/util.c +++ b/mm/util.c @@ -614,9 +614,12 @@ EXPORT_SYMBOL(kvmalloc_node); */ void kvfree(const void *addr) { - if (is_vmalloc_addr(addr)) - vfree(addr); - else + if (is_vmalloc_addr(addr)) { + if (in_atomic()) + vfree_atomic(); + else + vfree(addr); + } else kfree(addr); } EXPORT_SYMBOL(kvfree);
