From 33a154a96e71a34a1bcca9f40da343dbbf7b38b4 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Thu, 1 Oct 2026 14:52:55 +0000 Subject: selftests/bpf: Test packet range of pointers sharing an id Add tests where two packet pointers share an id and tightening one pointer's umax from its var_off would put it less than their constant distance from the other's umax: with an index & 0x38 capped at 50, the base pointer keeps umax 50, so the pointer 8 bytes further on must keep umax 58, even though its known bits allow at most 56. These refused a valid program or accepted an out-of-bounds access before the fix: - check the advanced copy, load through the base: valid, was refused; - check the base, load the byte at base + 1 through a copy advanced by 8: was accepted; - check base + 4, load 4 bytes at base + 2 through base + 8: reads two bytes past the checked range, was accepted; - the same as the second with data_meta pointers checked against data: was accepted. These pass with and without the fix and cover nearby paths: - subtract an unknown scalar from a checked pointer and load below it (the range is kept across a new id); - reach a load through two paths whose checks cover 8 and 7 bytes after the loaded pointer; the second path must not be pruned by the first; - spill a copy of a pointer, check the pointer, fill the copy and load one byte past the checked range: the load is refused, and the copy has the range of the check. Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20261001145255.855630-2-alexei.starovoitov@gmail.com Signed-off-by: Kumar Kartikeya Dwivedi --- lib/usercopy.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 81 insertions(+) create mode 100644 lib/usercopy.c (limited to 'lib/usercopy.c') diff --git a/lib/usercopy.c b/lib/usercopy.c new file mode 100644 index 000000000..e2f0bf104 --- /dev/null +++ b/lib/usercopy.c @@ -0,0 +1,81 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* out-of-line parts */ + +#if !defined(INLINE_COPY_USER) +unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n) +{ + return _inline_copy_from_user(to, from, n); +} +EXPORT_SYMBOL(_copy_from_user); + +unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n) +{ + return _inline_copy_to_user(to, from, n); +} +EXPORT_SYMBOL(_copy_to_user); +#endif + +/** + * check_zeroed_user: check if a userspace buffer only contains zero bytes + * @from: Source address, in userspace. + * @size: Size of buffer. + * + * This is effectively shorthand for "memchr_inv(from, 0, size) == NULL" for + * userspace addresses (and is more efficient because we don't care where the + * first non-zero byte is). + * + * Returns: + * * 0: There were non-zero bytes present in the buffer. + * * 1: The buffer was full of zero bytes. + * * -EFAULT: access to userspace failed. + */ +int check_zeroed_user(const void __user *from, size_t size) +{ + unsigned long val; + uintptr_t align = (uintptr_t) from % sizeof(unsigned long); + + if (unlikely(size == 0)) + return 1; + + from -= align; + size += align; + + if (!user_read_access_begin(from, size)) + return -EFAULT; + + unsafe_get_user(val, (unsigned long __user *) from, err_fault); + if (align) + val &= ~aligned_byte_mask(align); + + while (size > sizeof(unsigned long)) { + if (unlikely(val)) + goto done; + + from += sizeof(unsigned long); + size -= sizeof(unsigned long); + + unsafe_get_user(val, (unsigned long __user *) from, err_fault); + } + + if (size < sizeof(unsigned long)) + val &= aligned_byte_mask(size); + +done: + user_read_access_end(); + return (val == 0); +err_fault: + user_read_access_end(); + return -EFAULT; +} +EXPORT_SYMBOL(check_zeroed_user); -- cgit v1.3.1