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2045cdfa1b
Loading the nf_conntrack module with doubled hashsize parameter, i.e. modprobe nf_conntrack hashsize=12345 hashsize=12345 causes NULL-ptr deref. If 'hashsize' specified twice, the nf_conntrack_set_hashsize() function will be called also twice. The first nf_conntrack_set_hashsize() call will set the 'nf_conntrack_htable_size' variable: nf_conntrack_set_hashsize() ... /* On boot, we can set this without any fancy locking. */ if (!nf_conntrack_htable_size) return param_set_uint(val, kp); But on the second invocation, the nf_conntrack_htable_size is already set, so the nf_conntrack_set_hashsize() will take a different path and call the nf_conntrack_hash_resize() function. Which will crash on the attempt to dereference 'nf_conntrack_hash' pointer: BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 RIP: 0010:nf_conntrack_hash_resize+0x255/0x490 [nf_conntrack] Call Trace: nf_conntrack_set_hashsize+0xcd/0x100 [nf_conntrack] parse_args+0x1f9/0x5a0 load_module+0x1281/0x1a50 __se_sys_finit_module+0xbe/0xf0 do_syscall_64+0x7c/0x390 entry_SYSCALL_64_after_hwframe+0x49/0xbe Fix this, by checking !nf_conntrack_hash instead of !nf_conntrack_htable_size. nf_conntrack_hash will be initialized only after the module loaded, so the second invocation of the nf_conntrack_set_hashsize() won't crash, it will just reinitialize nf_conntrack_htable_size again. Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.