4.20-stable review patch. If anyone has any objections, please let me know.
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From: Ralph Campbell rcampbell@nvidia.com
commit 050c17f239fd53adb55aa768d4f41bc76c0fe045 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...
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
--- mm/mempolicy.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1314,7 +1314,7 @@ static int copy_nodes_to_user(unsigned l nodemask_t *nodes) { unsigned long copy = ALIGN(maxnode-1, 64) / 8; - const int nbytes = BITS_TO_LONGS(MAX_NUMNODES) * sizeof(long); + unsigned int nbytes = BITS_TO_LONGS(nr_node_ids) * sizeof(long);
if (copy > nbytes) { if (copy > PAGE_SIZE) @@ -1491,7 +1491,7 @@ static int kernel_get_mempolicy(int __us int uninitialized_var(pval); nodemask_t nodes;
- if (nmask != NULL && maxnode < MAX_NUMNODES) + if (nmask != NULL && maxnode < nr_node_ids) return -EINVAL;
err = do_get_mempolicy(&pval, &nodes, addr, flags); @@ -1527,7 +1527,7 @@ COMPAT_SYSCALL_DEFINE5(get_mempolicy, in unsigned long nr_bits, alloc_size; DECLARE_BITMAP(bm, MAX_NUMNODES);
- nr_bits = min_t(unsigned long, maxnode-1, MAX_NUMNODES); + nr_bits = min_t(unsigned long, maxnode-1, nr_node_ids); alloc_size = ALIGN(nr_bits, BITS_PER_LONG) / 8;
if (nmask)