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| author | Ali Ahmet Memis <ali@iusegentoo.com> | 2026-08-21 01:45:27 +0000 |
|---|---|---|
| committer | Stafford Horne <shorne@gmail.com> | 2026-08-29 07:32:26 +0100 |
| commit | 78004e9a87f240df03e2f73120d291763c32e0a7 (patch) | |
| tree | 137c22dd795222931b9d2bf2501d37cd766741aa /Documentation/filesystems/ext4/blockmap.rst | |
| download | linux-stable-78004e9a87f240df03e2f73120d291763c32e0a7.tar.gz linux-stable-78004e9a87f240df03e2f73120d291763c32e0a7.zip | |
openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted
sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.
l.lwz r29,0(r4)
l.lwz r27,0(r5)
l.sw 0(r4),r27
l.sw 0(r5),r29
The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.
A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.
This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.
Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.
[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>
Diffstat (limited to 'Documentation/filesystems/ext4/blockmap.rst')
| -rw-r--r-- | Documentation/filesystems/ext4/blockmap.rst | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/Documentation/filesystems/ext4/blockmap.rst b/Documentation/filesystems/ext4/blockmap.rst new file mode 100644 index 000000000..cc596541c --- /dev/null +++ b/Documentation/filesystems/ext4/blockmap.rst @@ -0,0 +1,49 @@ +.. SPDX-License-Identifier: GPL-2.0 + ++---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ +| i.i_block Offset | Where It Points | ++=====================+==============================================================================================================================================================================================================================+ +| 0 to 11 | Direct map to file blocks 0 to 11. | ++---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ +| 12 | Indirect block: (file blocks 12 to (``$block_size`` / 4) + 11, or 12 to 1035 if 4KiB blocks) | +| | | +| | +------------------------------+--------------------------------------------------------------------+ | +| | | Indirect Block Offset | Where It Points | | +| | +==============================+====================================================================+ | +| | | 0 to (``$block_size`` / 4) | Direct map to (``$block_size`` / 4) blocks (1024 if 4KiB blocks) | | +| | +------------------------------+--------------------------------------------------------------------+ | ++---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ +| 13 | Double-indirect block: (file blocks ``$block_size``/4 + 12 to (``$block_size`` / 4) ^ 2 + (``$block_size`` / 4) + 11, or 1036 to 1049611 if 4KiB blocks) | +| | | +| | +--------------------------------+---------------------------------------------------------------------------------------------------------+ | +| | | Double Indirect Block Offset | Where It Points | | +| | +================================+=========================================================================================================+ | +| | | 0 to (``$block_size`` / 4) | Map to (``$block_size`` / 4) indirect blocks (1024 if 4KiB blocks) | | +| | | | | | +| | | | +------------------------------+--------------------------------------------------------------------+ | | +| | | | | Indirect Block Offset | Where It Points | | | +| | | | +==============================+====================================================================+ | | +| | | | | 0 to (``$block_size`` / 4) | Direct map to (``$block_size`` / 4) blocks (1024 if 4KiB blocks) | | | +| | | | +------------------------------+--------------------------------------------------------------------+ | | +| | +--------------------------------+---------------------------------------------------------------------------------------------------------+ | ++---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ +| 14 | Triple-indirect block: (file blocks (``$block_size`` / 4) ^ 2 + (``$block_size`` / 4) + 12 to (``$block_size`` / 4) ^ 3 + (``$block_size`` / 4) ^ 2 + (``$block_size`` / 4) + 12, or 1049612 to 1074791436 if 4KiB blocks) | +| | | +| | +--------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+ | +| | | Triple Indirect Block Offset | Where It Points | | +| | +================================+================================================================================================================================================+ | +| | | 0 to (``$block_size`` / 4) | Map to (``$block_size`` / 4) double indirect blocks (1024 if 4KiB blocks) | | +| | | | | | +| | | | +--------------------------------+---------------------------------------------------------------------------------------------------------+ | | +| | | | | Double Indirect Block Offset | Where It Points | | | +| | | | +================================+=========================================================================================================+ | | +| | | | | 0 to (``$block_size`` / 4) | Map to (``$block_size`` / 4) indirect blocks (1024 if 4KiB blocks) | | | +| | | | | | | | | +| | | | | | +------------------------------+--------------------------------------------------------------------+ | | | +| | | | | | | Indirect Block Offset | Where It Points | | | | +| | | | | | +==============================+====================================================================+ | | | +| | | | | | | 0 to (``$block_size`` / 4) | Direct map to (``$block_size`` / 4) blocks (1024 if 4KiB blocks) | | | | +| | | | | | +------------------------------+--------------------------------------------------------------------+ | | | +| | | | +--------------------------------+---------------------------------------------------------------------------------------------------------+ | | +| | +--------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+ | ++---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ |