0efc5990bc
Another ambiguous use of strncpy() is to copy from strings that may not be NUL-terminated. These cases depend on having the destination buffer be explicitly larger than the source buffer's maximum size, having the size of the copy exactly match the source buffer's maximum size, and for the destination buffer to get explicitly NUL terminated. This usually happens when parsing protocols or hardware character arrays that are not guaranteed to be NUL-terminated. The code pattern is effectively this: char dest[sizeof(src) + 1]; strncpy(dest, src, sizeof(src)); dest[sizeof(dest) - 1] = '\0'; In practice it usually looks like: struct from_hardware { ... char name[HW_NAME_SIZE] __nonstring; ... }; struct from_hardware *p = ...; char name[HW_NAME_SIZE + 1]; strncpy(name, p->name, HW_NAME_SIZE); name[NW_NAME_SIZE] = '\0'; This cannot be replaced with: strscpy(name, p->name, sizeof(name)); because p->name is smaller and not NUL-terminated, so FORTIFY will trigger when strnlen(p->name, sizeof(name)) is used. And it cannot be replaced with: strscpy(name, p->name, sizeof(p->name)); because then "name" may contain a 1 character early truncation of p->name. Provide an unambiguous interface for converting a maybe not-NUL-terminated string to a NUL-terminated string, with compile-time buffer size checking so that it can never fail at runtime: memtostr() and memtostr_pad(). Also add KUnit tests for both. Link: https://lore.kernel.org/r/20240410023155.2100422-1-keescook@chromium.org Signed-off-by: Kees Cook <keescook@chromium.org> |
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arch | ||
block | ||
certs | ||
crypto | ||
Documentation | ||
drivers | ||
fs | ||
include | ||
init | ||
io_uring | ||
ipc | ||
kernel | ||
lib | ||
LICENSES | ||
mm | ||
net | ||
rust | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.clang-format | ||
.cocciconfig | ||
.editorconfig | ||
.get_maintainer.ignore | ||
.gitattributes | ||
.gitignore | ||
.mailmap | ||
.rustfmt.toml | ||
COPYING | ||
CREDITS | ||
Kbuild | ||
Kconfig | ||
MAINTAINERS | ||
Makefile | ||
README |
Linux kernel ============ There are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. Please read Documentation/admin-guide/README.rst first. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. The formatted documentation can also be read online at: https://www.kernel.org/doc/html/latest/ There are various text files in the Documentation/ subdirectory, several of them using the reStructuredText markup notation. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.