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authorCong Wang <cong.wang@bytedance.com>2021-02-18 03:16:47 +0300
committerDaniel Borkmann <daniel@iogearbox.net>2021-02-22 20:08:35 +0300
commit53f523f3052ac16bbc7718032aa6b848f971d28c (patch)
tree1d951cf69b3fb286484999fb30086bca1a4e3d4c /kernel/bpf
parent33ccec5fd740d0d5b78b77846f76eb5b4feb4327 (diff)
downloadlinux-53f523f3052ac16bbc7718032aa6b848f971d28c.tar.xz
bpf: Clear percpu pointers in bpf_prog_clone_free()
Similar to bpf_prog_realloc(), bpf_prog_clone_create() also copies the percpu pointers, but the clone still shares them with the original prog, so we have to clear these two percpu pointers in bpf_prog_clone_free(). Otherwise we would get a double free: BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI CPU: 13 PID: 8140 Comm: kworker/13:247 Kdump: loaded Tainted: G                W    OE   5.11.0-rc4.bm.1-amd64+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 test_bpf: #1 TXA Workqueue: events bpf_prog_free_deferred RIP: 0010:percpu_ref_get_many.constprop.97+0x42/0xf0 Code: [...] RSP: 0018:ffffa6bce1f9bda0 EFLAGS: 00010002 RAX: 0000000000000001 RBX: 0000000000000000 RCX: 00000000021dfc7b RDX: ffffffffae2eeb90 RSI: 867f92637e338da5 RDI: 0000000000000046 RBP: ffffa6bce1f9bda8 R08: 0000000000000000 R09: 0000000000000001 R10: 0000000000000046 R11: 0000000000000000 R12: 0000000000000280 R13: 0000000000000000 R14: 0000000000000000 R15: ffff9b5f3ffdedc0 FS:    0000000000000000(0000) GS:ffff9b5f2fb40000(0000) knlGS:0000000000000000 CS:    0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 000000027c36c002 CR4: 00000000003706e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace:     refill_obj_stock+0x5e/0xd0     free_percpu+0xee/0x550     __bpf_prog_free+0x4d/0x60     process_one_work+0x26a/0x590     worker_thread+0x3c/0x390     ? process_one_work+0x590/0x590     kthread+0x130/0x150     ? kthread_park+0x80/0x80     ret_from_fork+0x1f/0x30 This bug is 100% reproducible with test_kmod.sh. Fixes: 700d4796ef59 ("bpf: Optimize program stats") Fixes: ca06f55b9002 ("bpf: Add per-program recursion prevention mechanism") Reported-by: Jiang Wang <jiang.wang@bytedance.com> Signed-off-by: Cong Wang <cong.wang@bytedance.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20210218001647.71631-1-xiyou.wangcong@gmail.com
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/core.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 0ae015ad1e05..aa1e64196d8d 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1118,6 +1118,8 @@ static void bpf_prog_clone_free(struct bpf_prog *fp)
* clone is guaranteed to not be locked.
*/
fp->aux = NULL;
+ fp->stats = NULL;
+ fp->active = NULL;
__bpf_prog_free(fp);
}