Richard Yao a51288aabb Fix unsafe string operations
Coverity caught unsafe use of `strcpy()` in `ztest_dmu_objset_own()`,
`nfs_init_tmpfile()` and `dump_snapshot()`. It also caught an unsafe use
of `strlcat()` in `nfs_init_tmpfile()`.

Inspired by this, I did an audit of every single usage of `strcpy()` and
`strcat()` in the code. If I could not prove that the usage was safe, I
changed the code to use either `strlcpy()` or `strlcat()`, depending on
which function was originally used. In some cases, `snprintf()` was used
to replace multiple uses of `strcat` because it was cleaner.

Whenever I changed a function, I preferred to use `sizeof(dst)` when the
compiler is able to provide the string size via that. When it could not
because the string was passed by a caller, I checked the entire call
tree of the function to find out how big the buffer was and hard coded
it. Hardcoding is less than ideal, but it is safe unless someone shrinks
the buffer sizes being passed.

Additionally, Coverity reported three more string related issues:

 * It caught a case where we do an overlapping memory copy in a call to
   `snprintf()`. We fix that via `kmem_strdup()` and `kmem_strfree()`.

 * It caught `sizeof (buf)` being used instead of `buflen` in
   `zdb_nicenum()`'s call to `zfs_nicenum()`, which is passed to
   `snprintf()`. We change that to pass `buflen`.

 * It caught a theoretical unterminated string passed to `strcmp()`.
   This one is likely a false positive, but we have the information
   needed to do this more safely, so we change this to silence the false
   positive not just in coverity, but potentially other static analysis
   tools too. We switch to `strncmp()`.

 * There was a false positive in tests/zfs-tests/cmd/dir_rd_update.c. We
   suppress it by switching to `snprintf()` since other static analysis
   tools might complain about it too. Interestingly, there is a possible
   real bug there too, since it assumes that the passed directory path
   ends with '/'. We add a '/' to fix that potential bug.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Closes #13913
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OpenZFS is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the OpenZFS community. This repository contains the code for running OpenZFS on Linux and FreeBSD.

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Official Resources

Installation

Full documentation for installing OpenZFS on your favorite operating system can be found at the Getting Started Page.

Contribute & Develop

We have a separate document with contribution guidelines.

We have a Code of Conduct.

Release

OpenZFS is released under a CDDL license. For more details see the NOTICE, LICENSE and COPYRIGHT files; UCRL-CODE-235197

Supported Kernels

  • The META file contains the officially recognized supported Linux kernel versions.
  • Supported FreeBSD versions are any supported branches and releases starting from 12.2-RELEASE.
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