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commit 050c17f239 upstream.
The system call, get_mempolicy() [1], passes an unsigned long *nodemask
pointer and an unsigned long maxnode argument which specifies the length
of the user's nodemask array in bits (which is rounded up). The manual
page says that if the maxnode value is too small, get_mempolicy will
return EINVAL but there is no system call to return this minimum value.
To determine this value, some programs search /proc/<pid>/status for a
line starting with "Mems_allowed:" and use the number of digits in the
mask to determine the minimum value. A recent change to the way this line
is formatted [2] causes these programs to compute a value less than
MAX_NUMNODES so get_mempolicy() returns EINVAL.
Change get_mempolicy(), the older compat version of get_mempolicy(), and
the copy_nodes_to_user() function to use nr_node_ids instead of
MAX_NUMNODES, thus preserving the defacto method of computing the minimum
size for the nodemask array and the maxnode argument.
[1] http://man7.org/linux/man-pages/man2/get_mempolicy.2.html
[2] https://lore.kernel.org/lkml/1545405631-6808-1-git-send-email-longman@redhat.com
Link: http://lkml.kernel.org/r/20190211180245.22295-1-rcampbell@nvidia.com
Fixes: 4fb8e5b89bcbbbb ("include/linux/nodemask.h: use nr_node_ids (not MAX_NUMNODES) in __nodemask_pr_numnodes()")
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Suggested-by: Alexander Duyck <alexander.duyck@gmail.com>
Cc: Waiman Long <longman@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.