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Steven Rostedt (Google)
5677a3d713
Using strnlen(dest, str, n) is confusing, as the size of dest must be
strlen(dest) + n + 1. Even more confusing, using sizeof(string constant)
gives you strlen(string constant) + 1 and not just strlen().
These two together made using strncat() with a constant string a bit off
in the calculations as we have:
len = sizeof(HIST_PREFIX) + strlen(str) + 1;
kfree(last_cmd);
last_cmd = kzalloc(len, GFP_KERNEL);
strcpy(last_cmd, HIST_PREFIX);
len -= sizeof(HIST_PREFIX) + 1;
strncat(last_cmd, str, len);
The above works if we s/sizeof/strlen/ with HIST_PREFIX (which is defined
as "hist:", but because sizeof(HIST_PREFIX) is equal to
strlen(HIST_PREFIX) + 1, we can drop the +1 in the code. But at least
comment that we are doing so.
Link: https://lore.kernel.org/all/[email protected]/
Fixes: 9f8e5aee93 ("tracing: Fix allocation of last_cmd in last_cmd_set()")
Reported-by: kernel test robot <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>
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 Restructured Text 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.