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tcx: Fix splat during dev unregister

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During unregister_netdevice_many_notify(), the ordering of our concerned
function calls is like this:

  unregister_netdevice_many_notify
    dev_shutdown
	qdisc_put
            clsact_destroy
    tcx_uninstall

The syzbot reproducer triggered a case that the qdisc refcnt is not
zero during dev_shutdown().

tcx_uninstall() will then WARN_ON_ONCE(tcx_entry(entry)->miniq_active)
because the miniq is still active and the entry should not be freed.
The latter assumed that qdisc destruction happens before tcx teardown.

This fix is to avoid tcx_uninstall() doing tcx_entry_free() when the
miniq is still alive and let the clsact_destroy() do the free later, so
that we do not assume any specific ordering for either of them.

If still active, tcx_uninstall() does clear the entry when flushing out
the prog/link. clsact_destroy() will then notice the "!tcx_entry_is_active()"
and then does the tcx_entry_free() eventually.

Fixes: e420bed025 ("bpf: Add fd-based tcx multi-prog infra with link support")
Reported-by: syzbot+376a289e86a0fd02b9ba@syzkaller.appspotmail.com
Reported-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: syzbot+376a289e86a0fd02b9ba@syzkaller.appspotmail.com
Tested-by: Leon Romanovsky <leonro@nvidia.com>
Link: https://lore.kernel.org/r/222255fe07cb58f15ee662e7ee78328af5b438e4.1690549248.git.daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Martin KaFai Lau 2023-07-28 23:47:17 +02:00 committed by Jakub Kicinski
parent df41fa677d
commit 079082c60a
2 changed files with 24 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
include/linux/bpf_mprog.h
View File

@ -256,6 +256,22 @@ static inline void bpf_mprog_entry_copy(struct bpf_mprog_entry *dst,
memcpy(dst->fp_items, src->fp_items, sizeof(src->fp_items)); memcpy(dst->fp_items, src->fp_items, sizeof(src->fp_items));
} }
static inline void bpf_mprog_entry_clear(struct bpf_mprog_entry *dst)
{
memset(dst->fp_items, 0, sizeof(dst->fp_items));
}
static inline void bpf_mprog_clear_all(struct bpf_mprog_entry *entry,
struct bpf_mprog_entry **entry_new)
{
struct bpf_mprog_entry *peer;
peer = bpf_mprog_peer(entry);
bpf_mprog_entry_clear(peer);
peer->parent->count = 0;
*entry_new = peer;
}
static inline void bpf_mprog_entry_grow(struct bpf_mprog_entry *entry, int idx) static inline void bpf_mprog_entry_grow(struct bpf_mprog_entry *entry, int idx)
{ {
int total = bpf_mprog_total(entry); int total = bpf_mprog_total(entry);

12
kernel/bpf/tcx.c
View File

@ -94,15 +94,19 @@ out:
void tcx_uninstall(struct net_device *dev, bool ingress) void tcx_uninstall(struct net_device *dev, bool ingress)
{ {
struct bpf_mprog_entry *entry, *entry_new = NULL;
struct bpf_tuple tuple = {}; struct bpf_tuple tuple = {};
struct bpf_mprog_entry *entry;
struct bpf_mprog_fp *fp; struct bpf_mprog_fp *fp;
struct bpf_mprog_cp *cp; struct bpf_mprog_cp *cp;
bool active;
entry = tcx_entry_fetch(dev, ingress); entry = tcx_entry_fetch(dev, ingress);
if (!entry) if (!entry)
return; return;
tcx_entry_update(dev, NULL, ingress); active = tcx_entry(entry)->miniq_active;
if (active)
bpf_mprog_clear_all(entry, &entry_new);
tcx_entry_update(dev, entry_new, ingress);
tcx_entry_sync(); tcx_entry_sync();
bpf_mprog_foreach_tuple(entry, fp, cp, tuple) { bpf_mprog_foreach_tuple(entry, fp, cp, tuple) {
if (tuple.link) if (tuple.link)
@ -111,8 +115,8 @@ void tcx_uninstall(struct net_device *dev, bool ingress)
bpf_prog_put(tuple.prog); bpf_prog_put(tuple.prog);
tcx_skeys_dec(ingress); tcx_skeys_dec(ingress);
} }
WARN_ON_ONCE(tcx_entry(entry)->miniq_active); if (!active)
tcx_entry_free(entry); tcx_entry_free(entry);
} }
int tcx_prog_query(const union bpf_attr *attr, union bpf_attr __user *uattr) int tcx_prog_query(const union bpf_attr *attr, union bpf_attr __user *uattr)