CVE-2024-26868

MEDIUM
Published Apr 17, 2024 Modified Jan 14, 2025 CWE-476

Description

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: <TASK> ? __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 >>> 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 >>> prog.crashed_thread().stack_trace()[0]['idx'] (u32)1 >>> 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->mirror_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.

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CVSS v3.1 Score

5.5
MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor Product
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel

References

Frequently Asked Questions

What is CVE-2024-26868? +
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: <TASK> ? __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 >>> 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 >>> prog.crashed_thread().stack_trace()[0]['idx'] (u32)1 >>> 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->mirror_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. It has a CVSS v3.1 base score of 5.5 (MEDIUM).
How severe is CVE-2024-26868? +
CVE-2024-26868 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.
What products are affected by CVE-2024-26868? +
CVE-2024-26868 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.
How do I check if I'm vulnerable to CVE-2024-26868? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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