From: Wang Yufen wangyufen@huawei.com
mainline inclusion from mainline-v6.1-rc6 commit eb86559a691cea5fa63e57a03ec3dc9c31e97955 category: bugfix bugzilla: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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kmemleak reports this issue:
unreferenced object 0xffff88817139d000 (size 2048): comm "test_progs", pid 33246, jiffies 4307381979 (age 45851.820s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<0000000045f075f0>] kmalloc_trace+0x27/0xa0 [<0000000098b7c90a>] __check_func_call+0x316/0x1230 [<00000000b4c3c403>] check_helper_call+0x172e/0x4700 [<00000000aa3875b7>] do_check+0x21d8/0x45e0 [<000000001147357b>] do_check_common+0x767/0xaf0 [<00000000b5a595b4>] bpf_check+0x43e3/0x5bc0 [<0000000011e391b1>] bpf_prog_load+0xf26/0x1940 [<0000000007f765c0>] __sys_bpf+0xd2c/0x3650 [<00000000839815d6>] __x64_sys_bpf+0x75/0xc0 [<00000000946ee250>] do_syscall_64+0x3b/0x90 [<0000000000506b7f>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
The root case here is: In function prepare_func_exit(), the callee is not released in the abnormal scenario after "state->curframe--;". To fix, move "state->curframe--;" to the very bottom of the function, right when we free callee and reset frame[] pointer to NULL, as Andrii suggested.
In addition, function __check_func_call() has a similar problem. In the abnormal scenario before "state->curframe++;", the callee also should be released by free_func_state().
Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper") Fixes: fd978bf7fd31 ("bpf: Add reference tracking to verifier") Signed-off-by: Wang Yufen wangyufen@huawei.com Link: https://lore.kernel.org/r/1667884291-15666-1-git-send-email-wangyufen@huawei... Signed-off-by: Martin KaFai Lau martin.lau@kernel.org Conflicts: kernel/bpf/verifier.c [Resolve conflicts dut to __check_func_call() is not exists before refactor] Signed-off-by: Zheng Yejian zhengyejian1@huawei.com --- kernel/bpf/verifier.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 4f60168ce175..3282cfd505a7 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5430,7 +5430,7 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn, /* Transfer references to the callee */ err = copy_reference_state(callee, caller); if (err) - return err; + goto err_out;
/* copy r1 - r5 args that callee can access. The copy includes parent * pointers, which connects us up to the liveness chain @@ -5453,6 +5453,10 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn, print_verifier_state(env, callee); } return 0; +err_out: + free_func_state(callee); + state->frame[state->curframe + 1] = NULL; + return err; }
static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) @@ -5475,8 +5479,7 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) return -EINVAL; }
- state->curframe--; - caller = state->frame[state->curframe]; + caller = state->frame[state->curframe - 1]; /* return to the caller whatever r0 had in the callee */ caller->regs[BPF_REG_0] = *r0;
@@ -5494,7 +5497,7 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) } /* clear everything in the callee */ free_func_state(callee); - state->frame[state->curframe + 1] = NULL; + state->frame[state->curframe--] = NULL; return 0; }