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@zte.com.cn Reported-by: Minghao Chi chi.minghao@zte.com.cn Link: https://lore.kernel.org/all/20211222081026.484058-1-chi.minghao@zte.com.cn/ Fixes: fc37a3b8b438 ("[PATCH] ipc sem: use kvmalloc for sem_undo allocation") Cc: stable@vger.kernel.org Signed-off-by: Manfred Spraul manfred@colorfullife.com
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);}
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);