Patch "bpf: Fix memory leaks in __check_func_call" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    bpf: Fix memory leaks in __check_func_call

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bpf-fix-memory-leaks-in-__check_func_call.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 3d28f6afacfdedf56ae5911a7a8886a264b15303
Author: Wang Yufen <wangyufen@xxxxxxxxxx>
Date:   Tue Nov 8 13:11:31 2022 +0800

    bpf: Fix memory leaks in __check_func_call
    
    [ Upstream commit eb86559a691cea5fa63e57a03ec3dc9c31e97955 ]
    
    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@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/1667884291-15666-1-git-send-email-wangyufen@xxxxxxxxxx
    Signed-off-by: Martin KaFai Lau <martin.lau@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8a73a165ac76..cceb29b0585f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5808,11 +5808,11 @@ 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;
 
 	err = set_callee_state_cb(env, caller, callee, *insn_idx);
 	if (err)
-		return err;
+		goto err_out;
 
 	clear_caller_saved_regs(env, caller->regs);
 
@@ -5829,6 +5829,11 @@ 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;
 }
 
 int map_set_for_each_callback_args(struct bpf_verifier_env *env,
@@ -5966,8 +5971,7 @@ 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];
 	if (callee->in_callback_fn) {
 		/* enforce R0 return value range [0, 1]. */
 		struct tnum range = tnum_range(0, 1);
@@ -6006,7 +6010,7 @@ 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;
 }