{"id":"CVE-2021-47508","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: free exchange changeset on failures\n\nFstests runs on my VMs have show several kmemleak reports like the following.\n\n  unreferenced object 0xffff88811ae59080 (size 64):\n    comm \"xfs_io\", pid 12124, jiffies 4294987392 (age 6.368s)\n    hex dump (first 32 bytes):\n      00 c0 1c 00 00 00 00 00 ff cf 1c 00 00 00 00 00  ................\n      90 97 e5 1a 81 88 ff ff 90 97 e5 1a 81 88 ff ff  ................\n    backtrace:\n      [\u003c00000000ac0176d2\u003e] ulist_add_merge+0x60/0x150 [btrfs]\n      [\u003c0000000076e9f312\u003e] set_state_bits+0x86/0xc0 [btrfs]\n      [\u003c0000000014fe73d6\u003e] set_extent_bit+0x270/0x690 [btrfs]\n      [\u003c000000004f675208\u003e] set_record_extent_bits+0x19/0x20 [btrfs]\n      [\u003c00000000b96137b1\u003e] qgroup_reserve_data+0x274/0x310 [btrfs]\n      [\u003c0000000057e9dcbb\u003e] btrfs_check_data_free_space+0x5c/0xa0 [btrfs]\n      [\u003c0000000019c4511d\u003e] btrfs_delalloc_reserve_space+0x1b/0xa0 [btrfs]\n      [\u003c000000006d37e007\u003e] btrfs_dio_iomap_begin+0x415/0x970 [btrfs]\n      [\u003c00000000fb8a74b8\u003e] iomap_iter+0x161/0x1e0\n      [\u003c0000000071dff6ff\u003e] __iomap_dio_rw+0x1df/0x700\n      [\u003c000000002567ba53\u003e] iomap_dio_rw+0x5/0x20\n      [\u003c0000000072e555f8\u003e] btrfs_file_write_iter+0x290/0x530 [btrfs]\n      [\u003c000000005eb3d845\u003e] new_sync_write+0x106/0x180\n      [\u003c000000003fb505bf\u003e] vfs_write+0x24d/0x2f0\n      [\u003c000000009bb57d37\u003e] __x64_sys_pwrite64+0x69/0xa0\n      [\u003c000000003eba3fdf\u003e] do_syscall_64+0x43/0x90\n\nIn case brtfs_qgroup_reserve_data() or btrfs_delalloc_reserve_metadata()\nfail the allocated extent_changeset will not be freed.\n\nSo in btrfs_check_data_free_space() and btrfs_delalloc_reserve_space()\nfree the allocated extent_changeset to get rid of the allocated memory.\n\nThe issue currently only happens in the direct IO write path, but only\nafter 65b3c08606e5 (\"btrfs: fix ENOSPC failure when attempting direct IO\nwrite into NOCOW range\"), and also at defrag_one_locked_target(). Every\nother place is always calling extent_changeset_free() even if its call\nto btrfs_delalloc_reserve_space() or btrfs_check_data_free_space() has\nfailed.","modified":"2026-03-15T22:43:14.811752Z","published":"2024-05-24T15:15:11.573Z","related":["SUSE-SU-2024:2008-1","SUSE-SU-2024:2019-1","SUSE-SU-2024:2190-1"],"references":[{"type":"FIX","url":"https://git.kernel.org/stable/c/da5e817d9d75422eaaa05490d0b9a5e328fc1a51"},{"type":"FIX","url":"https://git.kernel.org/stable/c/ca06c5cb1b6dbfe67655b33c02fc394d65824519"}],"affected":[{"database_specific":{"unresolved_ranges":[{"events":[{"introduced":"0"},{"fixed":"5.15.8"}]},{"events":[{"introduced":"0"},{"last_affected":"5.16-rc1"}]},{"events":[{"introduced":"0"},{"last_affected":"5.16-rc2"}]},{"events":[{"introduced":"0"},{"last_affected":"5.16-rc3"}]},{"events":[{"introduced":"0"},{"last_affected":"5.16-rc4"}]}],"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-47508.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}