The patch titled
Subject: maple_tree: fix mas_empty_area_rev() null pointer dereference
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
maple_tree-fix-mas_empty_area_rev-null-pointer-dereference.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/maple_tree-fix-mas_empty_area_rev-null-pointer-dereference.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
Subject: maple_tree: fix mas_empty_area_rev() null pointer dereference
Date: Mon, 22 Apr 2024 16:33:49 -0400
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@xxxxxxxxxx
Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Reported-by: Marius Fleischer <fleischermarius@xxxxxxxxx>
Closes: https://lore.kernel.org/lkml/CAJg=8jyuSxDL6XvqEXY_66M20psRK2J53oBTP+fjV5xpW2-R6w@xxxxxxxxxxxxxx/
Link: https://lore.kernel.org/lkml/CAJg=8jyuSxDL6XvqEXY_66M20psRK2J53oBTP+fjV5xpW2-R6w@xxxxxxxxxxxxxx/
Tested-by: Marius Fleischer <fleischermarius@xxxxxxxxx>
Tested-by: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/maple_tree.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
--- a/lib/maple_tree.c~maple_tree-fix-mas_empty_area_rev-null-pointer-dereference
+++ a/lib/maple_tree.c
@@ -5109,18 +5109,18 @@ int mas_empty_area_rev(struct ma_state *
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;
_
Patches currently in -mm which might be from Liam.Howlett@xxxxxxxxxx are
maple_tree-fix-mas_empty_area_rev-null-pointer-dereference.patch
