medium CVSS 6.5

CVE-2021-47551·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: drm/amd/amdkfd: Fix kernel panic when reset failed and been triggered again In SRIOV configuration, the reset may failed to bring asic back to normal but stop cpsch already been called, the start_cpsch will not be called since there is no resume in this case. When reset been triggered again, driver should avoid to do uninitialization again.

Severity
medium
Software
Kernel
Fixed in
5.15.7
Published
2024-05-24

Affected versions

From: 5.11

Until: 5.15.7

Fixed in: 5.15.7

How to fix this CVE

Update your Linux kernel to version 5.15.7 or later to resolve a critical issue where failed ASIC resets in SRIOV configurations can cause kernel panics on subsequent reset attempts. The vulnerability stems from improper cleanup of CPU scheduler state when reset operations fail, leading to a crash if reset is retried. Apply the kernel update and reboot your system to ensure the fix is active.

sudo dnf upgrade kernel kernel-headers && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Check installed kernel version: uname -r — Verify it is 5.15.7 or later
  2. Confirm AMD KFD driver is loaded: lsmod | grep amdkfd — If present, the vulnerable component is in use
  3. Search kernel logs for reset failures: grep -i 'reset.*fail\|cpsch' /var/log/kern.log — Look for repeated reset attempts or scheduler state errors
  4. Verify patch application: grep -i '06c6f8f86ec243b89e52f0c3dc7062bcb9de74df' /boot/System.map-$(uname -r) — Confirm the fix commit is present in your kernel build

FAQ

What is CVE-2021-47551?

This vulnerability affects AMD KFD (Kernel Fusion Driver) in SRIOV virtualized environments where a failed ASIC reset leaves the CPU scheduler in an inconsistent state. When reset is triggered again without proper reinitialization, the kernel panics due to attempting to stop an already-stopped scheduler.

Is CVE-2021-47551 being actively exploited?

No, this vulnerability is not listed in CISA's Known Exploited Vulnerabilities catalog and has no public exploit code available. Exploitation requires local system access and specific SRIOV hardware configuration.

What versions of Kernel are affected by CVE-2021-47551?

Linux kernel versions 5.11 through 5.15.6 are vulnerable. Version 5.15.7 and later contain the fix.

How do I check if my server is vulnerable to CVE-2021-47551?

Run 'uname -r' and compare the output to version 5.15.7. If your version is between 5.11 and 5.15.6, you are vulnerable. Also verify AMD KFD is active with 'lsmod | grep amdkfd' and confirm SRIOV mode with 'cat /sys/module/amdgpu/parameters/sriov_vf_mode'.

Does Defensia detect CVE-2021-47551?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel is installed on a monitored server, CVE-2021-47551 will appear in your dashboard with remediation steps.

Related Kernel CVEs

CVE-2026-100075CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: RDMA/srpt: Fix srpt_alloc_rw_ctxs() unwind counters When srpt_alloc_rw_ctxs() fails partway through a multi-buffer indirect descriptor, the unwind path destroys RDMA contexts but leaves stale n_rw_ctx and n_rdma values (and a dangling rw_ctxs pointer). Later sq_wr_avail accounting in srpt_queue_response() or srpt_write_pending() can then subtract the wrong number of send queue credits. Reset the counters and clear rw_ctxs after freeing the heap allocation before returning an error.
CVE-2026-64439CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: crypto: krb5 - filter out async aead implementations at alloc krb5_aead_encrypt(), krb5_aead_decrypt() in rfc3961_simplified.c and rfc8009_encrypt(), rfc8009_decrypt() in rfc8009_aes2.c set a NULL completion callback and treat any negative return from crypto_aead_{encrypt,decrypt}() as terminal, falling through to kfree_sensitive(buffer). When the encrypt_name resolves to an async AEAD instance the request returns -EINPROGRESS, the buffer is freed while the backend's worker still holds a pointer, and the worker dereferences the freed slab on completion. KASAN report under UML+SLUB with a synthetic async aead backend bound to krb5->encrypt_name: BUG: KASAN: slab-use-after-free in t5_stub_complete+0x7d/0xc7 The helpers were written synchronously, so filter the async instances out at allocation time instead of plumbing crypto_wait_req() through every call site. Reachable via net/rxrpc/rxgk.c, fs/afs/cm_security.c and net/ceph/crypto.c on systems with an async AEAD provider bound to the krb5 enctype name.
CVE-2026-64066CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: netfs: Fix netfs_read_to_pagecache() to pause on subreq failure Fix netfs_read_to_pagecache() so that it pauses the generation of new subrequests if an already-issued subrequest fails.
CVE-2026-64383CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: smb: client: fix double-free in SMB2_flush() replay SMB2_flush() keeps its response buffer bookkeeping across replay attempts. If a replayable flush response is received and the retry then fails before cifs_send_recv() stores a replacement response, flush_exit will free the stale response pointer a second time. Reinitialize resp_buftype and rsp_iov at the top of the replay loop so cleanup only acts on response state produced by the current attempt. This fixes a double-free without changing replay handling for successful requests.
CVE-2026-64067CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: netfs: Fix missing barriers when accessing stream->subrequests locklessly The list of subrequests attached to stream->subrequests is accessed without locks by netfs_collect_read_results() and netfs_collect_write_results(), and then they access subreq->flags without taking a barrier after getting the subreq pointer from the list. Relatedly, the functions that build the list don't use any sort of write barrier when constructing the list to make sure that the NETFS_SREQ_IN_PROGRESS flag is perceived to be set first if no lock is taken. Fix this by: (1) Add a new list_add_tail_release() function that uses a release barrier to set the pointer to the new member of the list. (2) Add a new list_first_entry_or_null_acquire() function that uses an acquire barrier to read the pointer to the first member in a list (or return NULL). (3) Use list_add_tail_release() when adding a subreq to ->subrequests. (4) Use list_first_entry_or_null_acquire() when initially accessing the front of the list (when an item is removed, the pointer to the new front iterm is obtained under the same lock).

References

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