bpf: Free dynamically allocated bits in bpf_iter_bits_destroy()
bpf_iter_bits_destroy() uses "kit->nr_bits <= 64" to check whether the
bits are dynamically allocated. However, the check is incorrect and may
cause a kmemleak as shown below:
unreferenced object 0xffff88812628c8c0 (size 32):
comm "swapper/0", pid 1, jiffies 4294727320
hex dump (first 32 bytes):
b0 c1 55 f5 81 88 ff ff f0 f0 f0 f0 f0 f0 f0 f0 ..U...........
f0 f0 f0 f0 f0 f0 f0 f0 00 00 00 00 00 00 00 00 ..............
backtrace (crc 781e32cc):
[<00000000c452b4ab>] kmemleak_alloc+0x4b/0x80
[<0000000004e09f80>] __kmalloc_node_noprof+0x480/0x5c0
[<00000000597124d6>] __alloc.isra.0+0x89/0xb0
[<000000004ebfffcd>] alloc_bulk+0x2af/0x720
[<00000000d9c10145>] prefill_mem_cache+0x7f/0xb0
[<00000000ff9738ff>] bpf_mem_alloc_init+0x3e2/0x610
[<000000008b616eac>] bpf_global_ma_init+0x19/0x30
[<00000000fc473efc>] do_one_initcall+0xd3/0x3c0
[<00000000ec81498c>] kernel_init_freeable+0x66a/0x940
[<00000000b119f72f>] kernel_init+0x20/0x160
[<00000000f11ac9a7>] ret_from_fork+0x3c/0x70
[<0000000004671da4>] ret_from_fork_asm+0x1a/0x30
That is because nr_bits will be set as zero in bpf_iter_bits_next()
after all bits have been iterated.
Fix the issue by setting kit->bit to kit->nr_bits instead of setting
kit->nr_bits to zero when the iteration completes in
bpf_iter_bits_next(). In addition, use "!nr_bits || bits >= nr_bits" to
check whether the iteration is complete and still use "nr_bits > 64" to
indicate whether bits are dynamically allocated. The "!nr_bits" check is
necessary because bpf_iter_bits_new() may fail before setting
kit->nr_bits, and this condition will stop the iteration early instead
of accessing the zeroed or freed kit->bits.
Considering the initial value of kit->bits is -1 and the type of
kit->nr_bits is unsigned int, change the type of kit->nr_bits to int.
The potential overflow problem will be handled in the following patch.
Fixes: 4665415975
("bpf: Add bits iterator")
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20241030100516.3633640-2-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
parent
d0b98f6a17
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@ -2856,7 +2856,7 @@ struct bpf_iter_bits_kern {
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unsigned long *bits;
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unsigned long *bits;
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unsigned long bits_copy;
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unsigned long bits_copy;
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};
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};
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u32 nr_bits;
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int nr_bits;
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int bit;
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int bit;
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} __aligned(8);
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} __aligned(8);
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@ -2930,17 +2930,16 @@ bpf_iter_bits_new(struct bpf_iter_bits *it, const u64 *unsafe_ptr__ign, u32 nr_w
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__bpf_kfunc int *bpf_iter_bits_next(struct bpf_iter_bits *it)
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__bpf_kfunc int *bpf_iter_bits_next(struct bpf_iter_bits *it)
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{
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{
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struct bpf_iter_bits_kern *kit = (void *)it;
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struct bpf_iter_bits_kern *kit = (void *)it;
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u32 nr_bits = kit->nr_bits;
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int bit = kit->bit, nr_bits = kit->nr_bits;
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const unsigned long *bits;
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const unsigned long *bits;
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int bit;
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if (nr_bits == 0)
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if (!nr_bits || bit >= nr_bits)
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return NULL;
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return NULL;
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bits = nr_bits == 64 ? &kit->bits_copy : kit->bits;
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bits = nr_bits == 64 ? &kit->bits_copy : kit->bits;
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bit = find_next_bit(bits, nr_bits, kit->bit + 1);
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bit = find_next_bit(bits, nr_bits, bit + 1);
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if (bit >= nr_bits) {
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if (bit >= nr_bits) {
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kit->nr_bits = 0;
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kit->bit = bit;
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return NULL;
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return NULL;
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}
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}
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