[PATCH -next v2] bpf: Add oversize check before call kvmalloc()

Bixuan Cui
2021-12-01T01:33:35Z

Commit 7661809d493b ("mm: don't allow oversized kvmalloc() calls") add
the oversize check. When the allocation is larger than what kvmalloc()
supports, the following warning triggered:

WARNING: CPU: 1 PID: 372 at mm/util.c:597 kvmalloc_node+0x111/0x120
mm/util.c:597
Modules linked in:
CPU: 1 PID: 372 Comm: syz-executor.4 Not tainted 5.15.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:kvmalloc_node+0x111/0x120 mm/util.c:597
Code: 01 00 00 00 4c 89 e7 e8 7d f7 0c 00 49 89 c5 e9 69 ff ff ff e8 60
20 d1 ff 41 89 ed 41 81 cd 00 20 01 00 eb 95 e8 4f 20 d1 ff <0f> 0b e9
4c ff ff ff 0f 1f 84 00 00 00 00 00 55 48 89 fd 53 e8 36
RSP: 0018:ffffc90002bf7c98 EFLAGS: 00010216
RAX: 00000000000000ec RBX: 1ffff9200057ef9f RCX: ffffc9000ac63000
RDX: 0000000000040000 RSI: ffffffff81a6a621 RDI: 0000000000000003
RBP: 0000000000102cc0 R08: 000000007fffffff R09: 00000000ffffffff
R10: ffffffff81a6a5de R11: 0000000000000000 R12: 00000000ffff9aaa
R13: 0000000000000000 R14: 00000000ffffffff R15: 0000000000000000
FS: 00007f05f2573700(0000) GS:ffff8880b9d00000(0000)
knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2f424000 CR3: 0000000027d2c000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
kvmalloc include/linux/slab.h:741 [inline]
map_lookup_elem kernel/bpf/syscall.c:1090 [inline]
__sys_bpf+0x3a5b/0x5f00 kernel/bpf/syscall.c:4603
__do_sys_bpf kernel/bpf/syscall.c:4722 [inline]
__se_sys_bpf kernel/bpf/syscall.c:4720 [inline]
__x64_sys_bpf+0x75/0xb0 kernel/bpf/syscall.c:4720
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

The type of 'value_size' is u32, its value may exceed INT_MAX.

Reported-by: syzbot+cecf5b7071a0dfb76530@syzkaller.appspotmail.com
Signed-off-by: Bixuan Cui <cuibixuan@linux.alibaba.com>
---
Changes in v2:
* Change the err from -EINVAL to -E2BIG;
* Change "goto err_put" to "goto free_key";

kernel/bpf/syscall.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 1033ee8..30aabdd 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1094,6 +1094,10 @@ static int map_lookup_elem(union bpf_attr *attr)
}

value_size = bpf_map_value_size(map);
+ if (value_size > INT_MAX) {
+ err = -E2BIG;
+ goto free_key;
+ }

err = -ENOMEM;
value = kvmalloc(value_size, GFP_USER | __GFP_NOWARN);
--
1.8.3.1