CVE ID:	CVE-2024-26685
Description:	In the Linux kernel, the following vulnerability has been resolved: nilfs2: fix potential bug in end_buffer_async_write According to a syzbot report, end_buffer_async_write(), which handles the completion of block device writes, may detect abnormal condition of the buffer async_write flag and cause a BUG_ON failure when using nilfs2. Nilfs2 itself does not use end_buffer_async_write(). But, the async_write flag is now used as a marker by commit 7f42ec394156 ("nilfs2: fix issue with race condition of competition between segments for dirty blocks") as a means of resolving double list insertion of dirty blocks in nilfs_lookup_dirty_data_buffers() and nilfs_lookup_node_buffers() and the resulting crash. This modification is safe as long as it is used for file data and b-tree node blocks where the page caches are independent. However, it was irrelevant and redundant to also introduce async_write for segment summary and super root blocks that share buffers with the backing device. This led to the possibility that the BUG_ON check in end_buffer_async_write would fail as described above, if independent writebacks of the backing device occurred in parallel. The use of async_write for segment summary buffers has already been removed in a previous change. Fix this issue by removing the manipulation of the async_write flag for the remaining super root block buffer.
Test IDs:	None available
Cross References:	Common Vulnerability Exposure (CVE) ID: CVE-2024-26685 https://git.kernel.org/stable/c/2c3bdba00283a6c7a5b19481a59a730f46063803 https://git.kernel.org/stable/c/2c3bdba00283a6c7a5b19481a59a730f46063803 https://git.kernel.org/stable/c/5bc09b397cbf1221f8a8aacb1152650c9195b02b https://git.kernel.org/stable/c/5bc09b397cbf1221f8a8aacb1152650c9195b02b https://git.kernel.org/stable/c/626daab3811b772086aef1bf8eed3ffe6f523eff https://git.kernel.org/stable/c/626daab3811b772086aef1bf8eed3ffe6f523eff https://git.kernel.org/stable/c/6589f0f72f8edd1fa11adce4eedbd3615f2e78ab https://git.kernel.org/stable/c/6589f0f72f8edd1fa11adce4eedbd3615f2e78ab https://git.kernel.org/stable/c/8fa90634ec3e9cc50f42dd605eec60f2d146ced8 https://git.kernel.org/stable/c/8fa90634ec3e9cc50f42dd605eec60f2d146ced8 https://git.kernel.org/stable/c/c4a09fdac625e64abe478dcf88bfa20406616928 https://git.kernel.org/stable/c/c4a09fdac625e64abe478dcf88bfa20406616928 https://git.kernel.org/stable/c/d31c8721e816eff5ca6573cc487754f357c093cd https://git.kernel.org/stable/c/d31c8721e816eff5ca6573cc487754f357c093cd https://git.kernel.org/stable/c/f3e4963566f58726d3265a727116a42b591f6596 https://git.kernel.org/stable/c/f3e4963566f58726d3265a727116a42b591f6596