summaryrefslogtreecommitdiff
path: root/lib
diff options
context:
space:
mode:
authorLiam R. Howlett <Liam.Howlett@oracle.com>2024-04-22 23:33:49 +0300
committerAndrew Morton <akpm@linux-foundation.org>2024-05-06 03:28:05 +0300
commit955a923d2809803980ff574270f81510112be9cf (patch)
tree4f6026e03233204fd3bbc50d6d3abfb406a7d69b /lib
parentc88033efe9a391e72ba6b5df4b01d6e628f4e734 (diff)
downloadlinux-955a923d2809803980ff574270f81510112be9cf.tar.xz
maple_tree: fix mas_empty_area_rev() null pointer dereference
Currently the code calls mas_start() followed by mas_data_end() if the maple state is MA_START, but mas_start() may return with the maple state node == NULL. This will lead to a null pointer dereference when checking information in the NULL node, which is done in mas_data_end(). Avoid setting the offset if there is no node by waiting until after the maple state is checked for an empty or single entry state. A user could trigger the events to cause a kernel oops by unmapping all vmas to produce an empty maple tree, then mapping a vma that would cause the scenario described above. Link: https://lkml.kernel.org/r/20240422203349.2418465-1-Liam.Howlett@oracle.com Fixes: 54a611b60590 ("Maple Tree: add new data structure") Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com> Reported-by: Marius Fleischer <fleischermarius@gmail.com> Closes: https://lore.kernel.org/lkml/CAJg=8jyuSxDL6XvqEXY_66M20psRK2J53oBTP+fjV5xpW2-R6w@mail.gmail.com/ Link: https://lore.kernel.org/lkml/CAJg=8jyuSxDL6XvqEXY_66M20psRK2J53oBTP+fjV5xpW2-R6w@mail.gmail.com/ Tested-by: Marius Fleischer <fleischermarius@gmail.com> Tested-by: Sidhartha Kumar <sidhartha.kumar@oracle.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/maple_tree.c16
1 files changed, 8 insertions, 8 deletions
diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 55e1b35bf877..2d7d27e6ae3c 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5109,18 +5109,18 @@ int mas_empty_area_rev(struct ma_state *mas, unsigned long min,
if (size == 0 || max - min < size - 1)
return -EINVAL;
- if (mas_is_start(mas)) {
+ if (mas_is_start(mas))
mas_start(mas);
- mas->offset = mas_data_end(mas);
- } else if (mas->offset >= 2) {
- mas->offset -= 2;
- } else if (!mas_rewind_node(mas)) {
+ else if ((mas->offset < 2) && (!mas_rewind_node(mas)))
return -EBUSY;
- }
- /* Empty set. */
- if (mas_is_none(mas) || mas_is_ptr(mas))
+ if (unlikely(mas_is_none(mas) || mas_is_ptr(mas)))
return mas_sparse_area(mas, min, max, size, false);
+ else if (mas->offset >= 2)
+ mas->offset -= 2;
+ else
+ mas->offset = mas_data_end(mas);
+
/* The start of the window can only be within these values. */
mas->index = min;