Patch "bpf: add missing check_func_arg_reg_off() to prevent out-of-bounds memory accesses" has been added to the 6.10-stable tree

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

    bpf: add missing check_func_arg_reg_off() to prevent out-of-bounds memory accesses

to the 6.10-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-add-missing-check_func_arg_reg_off-to-prevent-ou.patch
and it can be found in the queue-6.10 subdirectory.

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



commit 48ece36104ccd87af1864d784b95b920e99a6b3a
Author: Matt Bobrowski <mattbobrowski@xxxxxxxxxx>
Date:   Tue Jun 25 06:28:56 2024 +0000

    bpf: add missing check_func_arg_reg_off() to prevent out-of-bounds memory accesses
    
    [ Upstream commit ec2b9a5e11e51fea1bb04c1e7e471952e887e874 ]
    
    Currently, it's possible to pass in a modified CONST_PTR_TO_DYNPTR to
    a global function as an argument. The adverse effects of this is that
    BPF helpers can continue to make use of this modified
    CONST_PTR_TO_DYNPTR from within the context of the global function,
    which can unintentionally result in out-of-bounds memory accesses and
    therefore compromise overall system stability i.e.
    
    [  244.157771] BUG: KASAN: slab-out-of-bounds in bpf_dynptr_data+0x137/0x140
    [  244.161345] Read of size 8 at addr ffff88810914be68 by task test_progs/302
    [  244.167151] CPU: 0 PID: 302 Comm: test_progs Tainted: G O E 6.10.0-rc3-00131-g66b586715063 #533
    [  244.174318] Call Trace:
    [  244.175787]  <TASK>
    [  244.177356]  dump_stack_lvl+0x66/0xa0
    [  244.179531]  print_report+0xce/0x670
    [  244.182314]  ? __virt_addr_valid+0x200/0x3e0
    [  244.184908]  kasan_report+0xd7/0x110
    [  244.187408]  ? bpf_dynptr_data+0x137/0x140
    [  244.189714]  ? bpf_dynptr_data+0x137/0x140
    [  244.192020]  bpf_dynptr_data+0x137/0x140
    [  244.194264]  bpf_prog_b02a02fdd2bdc5fa_global_call_bpf_dynptr_data+0x22/0x26
    [  244.198044]  bpf_prog_b0fe7b9d7dc3abde_callback_adjust_bpf_dynptr_reg_off+0x1f/0x23
    [  244.202136]  bpf_user_ringbuf_drain+0x2c7/0x570
    [  244.204744]  ? 0xffffffffc0009e58
    [  244.206593]  ? __pfx_bpf_user_ringbuf_drain+0x10/0x10
    [  244.209795]  bpf_prog_33ab33f6a804ba2d_user_ringbuf_callback_const_ptr_to_dynptr_reg_off+0x47/0x4b
    [  244.215922]  bpf_trampoline_6442502480+0x43/0xe3
    [  244.218691]  __x64_sys_prlimit64+0x9/0xf0
    [  244.220912]  do_syscall_64+0xc1/0x1d0
    [  244.223043]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
    [  244.226458] RIP: 0033:0x7ffa3eb8f059
    [  244.228582] Code: 08 89 e8 5b 5d c3 66 2e 0f 1f 84 00 00 00 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 8f 1d 0d 00 f7 d8 64 89 01 48
    [  244.241307] RSP: 002b:00007ffa3e9c6eb8 EFLAGS: 00000206 ORIG_RAX: 000000000000012e
    [  244.246474] RAX: ffffffffffffffda RBX: 00007ffa3e9c7cdc RCX: 00007ffa3eb8f059
    [  244.250478] RDX: 00007ffa3eb162b4 RSI: 0000000000000000 RDI: 00007ffa3e9c7fb0
    [  244.255396] RBP: 00007ffa3e9c6ed0 R08: 00007ffa3e9c76c0 R09: 0000000000000000
    [  244.260195] R10: 0000000000000000 R11: 0000000000000206 R12: ffffffffffffff80
    [  244.264201] R13: 000000000000001c R14: 00007ffc5d6b4260 R15: 00007ffa3e1c7000
    [  244.268303]  </TASK>
    
    Add a check_func_arg_reg_off() to the path in which the BPF verifier
    verifies the arguments of global function arguments, specifically
    those which take an argument of type ARG_PTR_TO_DYNPTR |
    MEM_RDONLY. Also, process_dynptr_func() doesn't appear to perform any
    explicit and strict type matching on the supplied register type, so
    let's also enforce that a register either type PTR_TO_STACK or
    CONST_PTR_TO_DYNPTR is by the caller.
    
    Reported-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
    Acked-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
    Acked-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
    Signed-off-by: Matt Bobrowski <mattbobrowski@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240625062857.92760-1-mattbobrowski@xxxxxxxxxx
    Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 6b422c275f78c..a8845cc299fec 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7716,6 +7716,13 @@ static int process_dynptr_func(struct bpf_verifier_env *env, int regno, int insn
 	struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
 	int err;
 
+	if (reg->type != PTR_TO_STACK && reg->type != CONST_PTR_TO_DYNPTR) {
+		verbose(env,
+			"arg#%d expected pointer to stack or const struct bpf_dynptr\n",
+			regno);
+		return -EINVAL;
+	}
+
 	/* MEM_UNINIT and MEM_RDONLY are exclusive, when applied to an
 	 * ARG_PTR_TO_DYNPTR (or ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_*):
 	 */
@@ -9465,6 +9472,10 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog,
 				return -EINVAL;
 			}
 		} else if (arg->arg_type == (ARG_PTR_TO_DYNPTR | MEM_RDONLY)) {
+			ret = check_func_arg_reg_off(env, reg, regno, ARG_PTR_TO_DYNPTR);
+			if (ret)
+				return ret;
+
 			ret = process_dynptr_func(env, regno, -1, arg->arg_type, 0);
 			if (ret)
 				return ret;
@@ -11958,12 +11969,6 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 			enum bpf_arg_type dynptr_arg_type = ARG_PTR_TO_DYNPTR;
 			int clone_ref_obj_id = 0;
 
-			if (reg->type != PTR_TO_STACK &&
-			    reg->type != CONST_PTR_TO_DYNPTR) {
-				verbose(env, "arg#%d expected pointer to stack or dynptr_ptr\n", i);
-				return -EINVAL;
-			}
-
 			if (reg->type == CONST_PTR_TO_DYNPTR)
 				dynptr_arg_type |= MEM_RDONLY;
 




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