{"id":"DEBIAN-CVE-2024-26868","details":"In the Linux kernel, the following vulnerability has been resolved:  nfs: fix panic when nfs4_ff_layout_prepare_ds() fails  We've been seeing the following panic in production  BUG: kernel NULL pointer dereference, address: 0000000000000065 PGD 2f485f067 P4D 2f485f067 PUD 2cc5d8067 PMD 0 RIP: 0010:ff_layout_cancel_io+0x3a/0x90 [nfs_layout_flexfiles] Call Trace:  \u003cTASK\u003e  ? __die+0x78/0xc0  ? page_fault_oops+0x286/0x380  ? __rpc_execute+0x2c3/0x470 [sunrpc]  ? rpc_new_task+0x42/0x1c0 [sunrpc]  ? exc_page_fault+0x5d/0x110  ? asm_exc_page_fault+0x22/0x30  ? ff_layout_free_layoutreturn+0x110/0x110 [nfs_layout_flexfiles]  ? ff_layout_cancel_io+0x3a/0x90 [nfs_layout_flexfiles]  ? ff_layout_cancel_io+0x6f/0x90 [nfs_layout_flexfiles]  pnfs_mark_matching_lsegs_return+0x1b0/0x360 [nfsv4]  pnfs_error_mark_layout_for_return+0x9e/0x110 [nfsv4]  ? ff_layout_send_layouterror+0x50/0x160 [nfs_layout_flexfiles]  nfs4_ff_layout_prepare_ds+0x11f/0x290 [nfs_layout_flexfiles]  ff_layout_pg_init_write+0xf0/0x1f0 [nfs_layout_flexfiles]  __nfs_pageio_add_request+0x154/0x6c0 [nfs]  nfs_pageio_add_request+0x26b/0x380 [nfs]  nfs_do_writepage+0x111/0x1e0 [nfs]  nfs_writepages_callback+0xf/0x30 [nfs]  write_cache_pages+0x17f/0x380  ? nfs_pageio_init_write+0x50/0x50 [nfs]  ? nfs_writepages+0x6d/0x210 [nfs]  ? nfs_writepages+0x6d/0x210 [nfs]  nfs_writepages+0x125/0x210 [nfs]  do_writepages+0x67/0x220  ? generic_perform_write+0x14b/0x210  filemap_fdatawrite_wbc+0x5b/0x80  file_write_and_wait_range+0x6d/0xc0  nfs_file_fsync+0x81/0x170 [nfs]  ? nfs_file_mmap+0x60/0x60 [nfs]  __x64_sys_fsync+0x53/0x90  do_syscall_64+0x3d/0x90  entry_SYSCALL_64_after_hwframe+0x46/0xb0  Inspecting the core with drgn I was able to pull this    \u003e\u003e\u003e prog.crashed_thread().stack_trace()[0]   #0 at 0xffffffffa079657a (ff_layout_cancel_io+0x3a/0x84) in ff_layout_cancel_io at fs/nfs/flexfilelayout/flexfilelayout.c:2021:27   \u003e\u003e\u003e prog.crashed_thread().stack_trace()[0]['idx']   (u32)1   \u003e\u003e\u003e prog.crashed_thread().stack_trace()[0]['flseg'].mirror_array[1].mirror_ds   (struct nfs4_ff_layout_ds *)0xffffffffffffffed  This is clear from the stack trace, we call nfs4_ff_layout_prepare_ds() which could error out initializing the mirror_ds, and then we go to clean it all up and our check is only for if (!mirror-\u003emirror_ds).  This is inconsistent with the rest of the users of mirror_ds, which have    if (IS_ERR_OR_NULL(mirror_ds))  to keep from tripping over this exact scenario.  Fix this up in ff_layout_cancel_io() to make sure we don't panic when we get an error. I also spot checked all the other instances of checking mirror_ds and we appear to be doing the correct checks everywhere, only unconditionally dereferencing mirror_ds when we know it would be valid.","modified":"2026-09-15T09:02:55.827838566Z","published":"2024-04-17T11:15:09.360Z","upstream":["CVE-2024-26868"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2024-26868"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.85-1"}]}],"versions":["6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-26868.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.7.12-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-26868.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.7.12-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-26868.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}