This is a note to let you know that I've just added the patch titled
security/keys: fix slab-out-of-bounds in key_task_permission
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
security-keys-fix-slab-out-of-bounds-in-key_task_per.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 2f46b1b0bffbb9997681eed25898d9f2ffc49480
Author: Chen Ridong <chenridong@xxxxxxxxxx>
Date: Tue Oct 8 12:46:39 2024 +0000
security/keys: fix slab-out-of-bounds in key_task_permission
[ Upstream commit 4a74da044ec9ec8679e6beccc4306b936b62873f ]
KASAN reports an out of bounds read:
BUG: KASAN: slab-out-of-bounds in __kuid_val include/linux/uidgid.h:36
BUG: KASAN: slab-out-of-bounds in uid_eq include/linux/uidgid.h:63 [inline]
BUG: KASAN: slab-out-of-bounds in key_task_permission+0x394/0x410
security/keys/permission.c:54
Read of size 4 at addr ffff88813c3ab618 by task stress-ng/4362
CPU: 2 PID: 4362 Comm: stress-ng Not tainted 5.10.0-14930-gafbffd6c3ede #15
Call Trace:
__dump_stack lib/dump_stack.c:82 [inline]
dump_stack+0x107/0x167 lib/dump_stack.c:123
print_address_description.constprop.0+0x19/0x170 mm/kasan/report.c:400
__kasan_report.cold+0x6c/0x84 mm/kasan/report.c:560
kasan_report+0x3a/0x50 mm/kasan/report.c:585
__kuid_val include/linux/uidgid.h:36 [inline]
uid_eq include/linux/uidgid.h:63 [inline]
key_task_permission+0x394/0x410 security/keys/permission.c:54
search_nested_keyrings+0x90e/0xe90 security/keys/keyring.c:793
This issue was also reported by syzbot.
It can be reproduced by following these steps(more details [1]):
1. Obtain more than 32 inputs that have similar hashes, which ends with the
pattern '0xxxxxxxe6'.
2. Reboot and add the keys obtained in step 1.
The reproducer demonstrates how this issue happened:
1. In the search_nested_keyrings function, when it iterates through the
slots in a node(below tag ascend_to_node), if the slot pointer is meta
and node->back_pointer != NULL(it means a root), it will proceed to
descend_to_node. However, there is an exception. If node is the root,
and one of the slots points to a shortcut, it will be treated as a
keyring.
2. Whether the ptr is keyring decided by keyring_ptr_is_keyring function.
However, KEYRING_PTR_SUBTYPE is 0x2UL, the same as
ASSOC_ARRAY_PTR_SUBTYPE_MASK.
3. When 32 keys with the similar hashes are added to the tree, the ROOT
has keys with hashes that are not similar (e.g. slot 0) and it splits
NODE A without using a shortcut. When NODE A is filled with keys that
all hashes are xxe6, the keys are similar, NODE A will split with a
shortcut. Finally, it forms the tree as shown below, where slot 6 points
to a shortcut.
NODE A
+------>+---+
ROOT | | 0 | xxe6
+---+ | +---+
xxxx | 0 | shortcut : : xxe6
+---+ | +---+
xxe6 : : | | | xxe6
+---+ | +---+
| 6 |---+ : : xxe6
+---+ +---+
xxe6 : : | f | xxe6
+---+ +---+
xxe6 | f |
+---+
4. As mentioned above, If a slot(slot 6) of the root points to a shortcut,
it may be mistakenly transferred to a key*, leading to a read
out-of-bounds read.
To fix this issue, one should jump to descend_to_node if the ptr is a
shortcut, regardless of whether the node is root or not.
[1] https://lore.kernel.org/linux-kernel/1cfa878e-8c7b-4570-8606-21daf5e13ce7@xxxxxxxxxxxxxxx/
[jarkko: tweaked the commit message a bit to have an appropriate closes
tag.]
Fixes: b2a4df200d57 ("KEYS: Expand the capacity of a keyring")
Reported-by: syzbot+5b415c07907a2990d1a3@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://lore.kernel.org/all/000000000000cbb7860611f61147@xxxxxxxxxx/T/
Signed-off-by: Chen Ridong <chenridong@xxxxxxxxxx>
Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 14abfe765b7e7..9f0fc81a3a7b9 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -772,8 +772,11 @@ static bool search_nested_keyrings(struct key *keyring,
for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
ptr = READ_ONCE(node->slots[slot]);
- if (assoc_array_ptr_is_meta(ptr) && node->back_pointer)
- goto descend_to_node;
+ if (assoc_array_ptr_is_meta(ptr)) {
+ if (node->back_pointer ||
+ assoc_array_ptr_is_shortcut(ptr))
+ goto descend_to_node;
+ }
if (!keyring_ptr_is_keyring(ptr))
continue;
