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selftests/bpf: Test overlapping dynptr copies on xdp frags

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Add dynptr tests for copies within one xdp packet with frags, where the
source and the destination overlap and the destination is above the
source:

- test_dynptr_copy_xdp_overlap: both ranges cross from the linear part
  into frag0. bpf_dynptr_copy() of 1200 bytes with the destination 100
  bytes above the source.
- test_dynptr_copy_xdp_overlap_src_linear: the source is in the linear
  part and the destination crosses into frag0.
- test_dynptr_copy_xdp_overlap_dst_frag: the source crosses into frag0
  and the destination is in frag0.

The new tests set err when the data is wrong. The existing
test_dynptr_copy_xdp does not, so it can pass on corrupted data.

Without the fix to bpf_dynptr_copy(), test_dynptr_copy_xdp_overlap
fails. With it, all the new tests pass.

Signed-off-by: Ayushman Rout <ayushmanrout27@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://patch.msgid.link/20261026162810.12862-3-ayushmanrout27@gmail.com
This commit is contained in:
Ayushman Rout 2026-10-26 21:58:09 +05:30 committed by Alexei Starovoitov
parent 696f0954e3
commit 8f92b56d22
No known key found for this signature in database
2 changed files with 93 additions and 0 deletions
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3
tools/testing/selftests/bpf/prog_tests/dynptr.c
View File

@ -22,6 +22,9 @@ static struct {
{"test_dynptr_data", SETUP_SYSCALL_SLEEP},
{"test_dynptr_copy", SETUP_SYSCALL_SLEEP},
{"test_dynptr_copy_xdp", SETUP_XDP_PROG},
{"test_dynptr_copy_xdp_overlap", SETUP_XDP_PROG},
{"test_dynptr_copy_xdp_overlap_src_linear", SETUP_XDP_PROG},
{"test_dynptr_copy_xdp_overlap_dst_frag", SETUP_XDP_PROG},
{"test_dynptr_memset_zero", SETUP_SYSCALL_SLEEP},
{"test_dynptr_memset_notzero", SETUP_SYSCALL_SLEEP},
{"test_dynptr_memset_zero_offset", SETUP_SYSCALL_SLEEP},

90
tools/testing/selftests/bpf/progs/dynptr_success.c
View File

@ -759,6 +759,96 @@ int test_dynptr_copy_xdp(struct xdp_md *xdp)
return XDP_DROP;
}
static __always_inline int fill_xdp(struct bpf_dynptr *ptr, __u32 start, __u32 n)
{
__u8 b;
int i;
bpf_for(i, 0, n) {
b = (start + i) % 251;
if (bpf_dynptr_write(ptr, start + i, &b, 1, 0))
return 1;
}
return 0;
}
static __always_inline int check_xdp(struct bpf_dynptr *ptr, __u32 at, __u32 n, __u32 from)
{
__u8 b;
int i;
bpf_for(i, 0, n) {
if (bpf_dynptr_read(&b, 1, ptr, at + i, 0))
return 1;
if (b != (__u8)((from + i) % 251))
return 1;
}
return 0;
}
SEC("?xdp")
int test_dynptr_copy_xdp_overlap(struct xdp_md *xdp)
{
void *data_end = (void *)(long)xdp->data_end;
void *data = (void *)(long)xdp->data;
__u32 off = data_end - data - 1000;
struct bpf_dynptr ptr;
bpf_dynptr_from_xdp(xdp, 0, &ptr);
if (fill_xdp(&ptr, off, 1300)) {
err = 1;
return XDP_DROP;
}
err = bpf_dynptr_copy(&ptr, off + 100, &ptr, off, 1200);
if (err)
return XDP_DROP;
if (check_xdp(&ptr, off + 100, 1200, off))
err = 2;
return XDP_DROP;
}
SEC("?xdp")
int test_dynptr_copy_xdp_overlap_src_linear(struct xdp_md *xdp)
{
void *data_end = (void *)(long)xdp->data_end;
void *data = (void *)(long)xdp->data;
__u32 lin = data_end - data;
struct bpf_dynptr ptr;
bpf_dynptr_from_xdp(xdp, 0, &ptr);
if (fill_xdp(&ptr, lin - 64, 118)) {
err = 1;
return XDP_DROP;
}
err = bpf_dynptr_copy(&ptr, lin - 10, &ptr, lin - 64, 64);
if (err)
return XDP_DROP;
if (check_xdp(&ptr, lin - 10, 64, lin - 64))
err = 2;
return XDP_DROP;
}
SEC("?xdp")
int test_dynptr_copy_xdp_overlap_dst_frag(struct xdp_md *xdp)
{
void *data_end = (void *)(long)xdp->data_end;
void *data = (void *)(long)xdp->data;
__u32 lin = data_end - data;
struct bpf_dynptr ptr;
bpf_dynptr_from_xdp(xdp, 0, &ptr);
if (fill_xdp(&ptr, lin - 10, 84)) {
err = 1;
return XDP_DROP;
}
err = bpf_dynptr_copy(&ptr, lin + 10, &ptr, lin - 10, 64);
if (err)
return XDP_DROP;
if (check_xdp(&ptr, lin + 10, 64, lin - 10))
err = 2;
return XDP_DROP;
}
char memset_zero_data[] = "data to be zeroed";
SEC("?tp/syscalls/sys_enter_nanosleep")