Description

In the Linux kernel, the following vulnerability has been resolved: netfs: Only call folio_start_fscache() one time for each folio If a network filesystem using netfs implements a clamp_length() function, it can set subrequest lengths smaller than a page size. When we loop through the folios in netfs_rreq_unlock_folios() to set any folios to be written back, we need to make sure we only call folio_start_fscache() once for each folio. Otherwise, this simple testcase: mount -o fsc,rsize=1024,wsize=1024 127.0.0.1:/export /mnt/nfs dd if=/dev/zero of=/mnt/nfs/file.bin bs=4096 count=1 1+0 records in 1+0 records out 4096 bytes (4.1 kB, 4.0 KiB) copied, 0.0126359 s, 324 kB/s echo 3 > /proc/sys/vm/drop_caches cat /mnt/nfs/file.bin > /dev/null will trigger an oops similar to the following: page dumped because: VM_BUG_ON_FOLIO(folio_test_private_2(folio)) ------------[ cut here ]------------ kernel BUG at include/linux/netfs.h:44! ... CPU: 5 PID: 134 Comm: kworker/u16:5 Kdump: loaded Not tainted 6.4.0-rc5 ... RIP: 0010:netfs_rreq_unlock_folios+0x68e/0x730 [netfs] ... Call Trace: netfs_rreq_assess+0x497/0x660 [netfs] netfs_subreq_terminated+0x32b/0x610 [netfs] nfs_netfs_read_completion+0x14e/0x1a0 [nfs] nfs_read_completion+0x2f9/0x330 [nfs] rpc_free_task+0x72/0xa0 [sunrpc] rpc_async_release+0x46/0x70 [sunrpc] process_one_work+0x3bd/0x710 worker_thread+0x89/0x610 kthread+0x181/0x1c0 ret_from_fork+0x29/0x50

Metrics

 

CVSS Version 4.0 CVSS Version 3.x CVSS Version 2.0

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CVSS 4.0 Severity and Vector Strings:

NIST: NVD

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CVSS 3.x Severity and Vector Strings:

NIST: NVD

Base Score:  N/A

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CVSS 2.0 Severity and Vector Strings:

NIST: NVD

Base Score: N/A

NVD assessment not yet provided.

In the Linux kernel, the following vulnerability has been resolved:

netfs: Only call folio_start_fscache() one time for each folio

If a network filesystem using netfs implements a clamp_length()
function, it can set subrequest lengths smaller than a page size.

When we loop through the folios in netfs_rreq_unlock_folios() to
set any folios to be written back, we need to make sure we only
call folio_start_fscache() once for each folio.

Otherwise, this simple testcase:

  mount -o fsc,rsize=102

Linux https://git.kernel.org/stable/c/d9f5537479d4ec97ea92ff24e81a517d5772581a [No types assigned]

Linux https://git.kernel.org/stable/c/df1c357f25d808e30b216188330e708e09e1a412 [No types assigned]

Linux https://git.kernel.org/stable/c/df9950d37df113db59495fa09d060754366a2b7c [No types assigned]