Hi Lorenzo, On Thu, May 15, 2025 at 03:01:56PM +0100, Lorenzo Stoakes wrote: > +cc Liam, Sid. > > Andrew - please drop this patch until this is fixed. > > Hi Jared, > > This breaks the xarray and vma userland testing. Please ensure that any > required stub are set up there to allow for your fix to work correctly. > > Once moved to mm-unstable, or at least -next this would get caught by bots > (hopefully :) so this is a mandatory pre-requisite to this being merged. Ouch, my bad! I'll make sure this is covered in v2. Thanks for catching that. Jared > > Cheers, Lorenzo > > P.S. Liam, Sid - do you think it might be useful to add us 3 as reviewers > to the xarray entry in MAINTAINERS so we pick up on this sooner? > > $ cd tools/testing/radix-tree > $ make > cp ../shared/autoconf.h generated/autoconf.h > cc -I../shared -I. -I../../include -I../../../lib -g -Og -Wall -D_LGPL_SOURCE -fsanitize=address -fsanitize=undefined -c -o main.o main.c > cc -c -I../shared -I. -I../../include -I../../../lib -g -Og -Wall -D_LGPL_SOURCE -fsanitize=address -fsanitize=undefined ../shared/xarray-shared.c -o xarray-shared.o > In file included from ../shared/xarray-shared.c:5: > ../shared/../../../lib/xarray.c: In function ‘xas_shrink’: > ../shared/../../../lib/xarray.c:480:17: error: implicit declaration of function ‘kmemleak_transient_leak’ [-Wimplicit-function-declaration] > 480 | kmemleak_transient_leak(node); > | ^~~~~~~~~~~~~~~~~~~~~~~ > make: *** [../shared/shared.mk:37: xarray-shared.o] Error 1 > $ cd ../vma > $ make > cc -c -I../shared -I. -I../../include -I../../../lib -g -Og -Wall -D_LGPL_SOURCE -fsanitize=address -fsanitize=undefined ../shared/xarray-shared.c -o xarray-shared.o > In file included from ../shared/xarray-shared.c:5: > ../shared/../../../lib/xarray.c: In function ‘xas_shrink’: > ../shared/../../../lib/xarray.c:480:17: error: implicit declaration of function ‘kmemleak_transient_leak’ [-Wimplicit-function-declaration] > 480 | kmemleak_transient_leak(node); > | ^~~~~~~~~~~~~~~~~~~~~~~ > make: *** [../shared/shared.mk:37: xarray-shared.o] Error 1 > > On Mon, May 12, 2025 at 12:17:07PM -0700, Jared Kangas wrote: > > Kmemleak periodically produces a false positive report that resembles > > the following: > > > > unreferenced object 0xffff0000c105ed08 (size 576): > > comm "swapper/0", pid 1, jiffies 4294937478 > > hex dump (first 32 bytes): > > 00 00 03 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > > d8 e7 0a 8b 00 80 ff ff 20 ed 05 c1 00 00 ff ff ........ ....... > > backtrace (crc 69e99671): > > kmemleak_alloc+0xb4/0xc4 > > kmem_cache_alloc_lru+0x1f0/0x244 > > xas_alloc+0x2a0/0x3a0 > > xas_expand.constprop.0+0x144/0x4dc > > xas_create+0x2b0/0x484 > > xas_store+0x60/0xa00 > > __xa_alloc+0x194/0x280 > > __xa_alloc_cyclic+0x104/0x2e0 > > dev_index_reserve+0xd8/0x18c > > register_netdevice+0x5e8/0xf90 > > register_netdev+0x28/0x50 > > loopback_net_init+0x68/0x114 > > ops_init+0x90/0x2c0 > > register_pernet_operations+0x20c/0x554 > > register_pernet_device+0x3c/0x8c > > net_dev_init+0x5cc/0x7d8 > > > > This transient leak can be traced to xas_shrink(): when the xarray's > > head is reassigned, kmemleak may have already started scanning the > > xarray. When this happens, if kmemleak fails to scan the new xa_head > > before it moves, kmemleak will see it as a leak until the xarray is > > scanned again. > > > > The report can be reproduced by running the xdp_bonding BPF selftest, > > although it doesn't appear consistently due to the bug's transience. > > In my testing, the following script has reliably triggered the report in > > under an hour on a debug kernel with kmemleak enabled, where KSELFTESTS > > is set to the install path for the kernel selftests: > > > > #!/bin/sh > > set -eu > > > > echo 1 >/sys/module/kmemleak/parameters/verbose > > echo scan=1 >/sys/kernel/debug/kmemleak > > > > while :; do > > $KSELFTESTS/bpf/test_progs -t xdp_bonding > > done > > > > To prevent this false positive report, mark the new xa_head in > > xas_shrink() as a transient leak. > > > > Signed-off-by: Jared Kangas <jkangas@xxxxxxxxxx> > > --- > > lib/xarray.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/lib/xarray.c b/lib/xarray.c > > index 9644b18af18d1..51314fa157b31 100644 > > --- a/lib/xarray.c > > +++ b/lib/xarray.c > > @@ -8,6 +8,7 @@ > > > > #include <linux/bitmap.h> > > #include <linux/export.h> > > +#include <linux/kmemleak.h> > > #include <linux/list.h> > > #include <linux/slab.h> > > #include <linux/xarray.h> > > @@ -476,6 +477,7 @@ static void xas_shrink(struct xa_state *xas) > > break; > > node = xa_to_node(entry); > > node->parent = NULL; > > + kmemleak_transient_leak(node); > > } > > } > > > > -- > > 2.49.0 > > > > > > >
