bpf: Use strncpy_from_unsafe_strict() in bpf_seq_printf() helper

In bpf_seq_printf() helper, when user specified a "%s" in the
format string, strncpy_from_unsafe() is used to read the actual string
to a buffer. The string could be a format string or a string in
the kernel data structure. It is really unlikely that the string
will reside in the user memory.

This is different from Commit b2a5212fb634 ("bpf: Restrict bpf_trace_printk()'s %s
usage and add %pks, %pus specifier") which still used
strncpy_from_unsafe() for "%s" to preserve the old behavior.

If in the future, bpf_seq_printf() indeed needs to read user
memory, we can implement "%pus" format string.

Based on discussion in [1], if the intent is to read kernel memory,
strncpy_from_unsafe_strict() should be used. So this patch
changed to use strncpy_from_unsafe_strict().

[1]: https://lore.kernel.org/bpf/[email protected]/T/

Fixes: 492e639f0c22 ("bpf: Add bpf_seq_printf and bpf_seq_write helpers")
Signed-off-by: Yonghong Song <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
Acked-by: Song Liu <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

0 files changed, 0 insertions, 0 deletions