high CVSS 7.8

CVE-2021-47549·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: sata_fsl: fix UAF in sata_fsl_port_stop when rmmod sata_fsl When the `rmmod sata_fsl.ko` command is executed in the PPC64 GNU/Linux, a bug is reported: ================================================================== BUG: Unable to handle kernel data access on read at 0x80000800805b502c Oops: Kernel access of bad area, sig: 11 [#1] NIP [c0000000000388a4] .ioread32+0x4/0x20 LR [80000000000c6034] .sata_fsl_port_stop+0x44/0xe0 [sata_fsl] Call Trace: .free_irq+0x1c/0x4e0 (unreliable) .ata_host_stop+0x74/0xd0 [libata] .release_nodes+0x330/0x3f0 .device_release_driver_internal+0x178/0x2c0 .driver_detach+0x64/0xd0 .bus_remove_driver+0x70/0xf0 .driver_unregister+0x38/0x80 .platform_driver_unregister+0x14/0x30 .fsl_sata_driver_exit+0x18/0xa20 [sata_fsl] .__se_sys_delete_module+0x1ec/0x2d0 .system_call_exception+0xfc/0x1f0 system_call_common+0xf8/0x200 ================================================================== The triggering of the BUG is shown in the following stack: driver_detach device_release_driver_internal __device_release_driver drv->remove(dev) --> platform_drv_remove/platform_remove drv->remove(dev) --> sata_fsl_remove iounmap(host_priv->hcr_base); <---- unmap kfree(host_priv); <---- free devres_release_all release_nodes dr->node.release(dev, dr->data) --> ata_host_stop ap->ops->port_stop(ap) --> sata_fsl_port_stop ioread32(hcr_base + HCONTROL) <---- UAF host->ops->host_stop(host) The iounmap(host_priv->hcr_base) and kfree(host_priv) functions should not be executed in drv->remove. These functions should be executed in host_stop after port_stop. Therefore, we move these functions to the new function sata_fsl_host_stop and bind the new function to host_stop.

Severity
high
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 fix a use-after-free vulnerability in the sata_fsl SATA driver that occurs during module unload. This vulnerability affects systems running kernel versions 5.11 through 5.15.6 and causes kernel panics when removing the sata_fsl driver. Apply the kernel update promptly, especially on PPC64 systems where this driver is commonly used.

sudo dnf update kernel kernel-devel kernel-headers

Defensia detects this vulnerability

How to check if you are affected

  1. Check kernel version: uname -r | grep -E '^5\.(11|12|13|14|15\.[0-6])'
  2. Verify sata_fsl driver availability: lsmod | grep sata_fsl (if output appears, the driver is loaded)
  3. Check system architecture: uname -m (vulnerability primarily affects ppc64, but patch applies to all architectures)
  4. After patching, verify new kernel: uname -r should show version 5.15.7 or later; test driver removal: sudo modprobe -r sata_fsl && dmesg | tail -20 (should show clean removal without kernel access errors)

FAQ

What is CVE-2021-47549?

CVE-2021-47549 is a use-after-free vulnerability in the Linux kernel's sata_fsl SATA driver that occurs during module unload. When rmmod is executed on sata_fsl.ko, the driver attempts to access memory regions that have already been freed, triggering a kernel panic with a data access exception.

Is CVE-2021-47549 being actively exploited?

No, CVE-2021-47549 is not actively exploited in the wild and no public exploits are available. However, any administrator who unloads the sata_fsl module will trigger the crash, making it a practical denial-of-service issue.

What versions of Kernel are affected by CVE-2021-47549?

Kernel versions 5.11 through 5.15.6 are affected. The vulnerability was fixed in kernel 5.15.7 and all subsequent releases.

How do I check if my server is vulnerable to CVE-2021-47549?

Run uname -r and verify the output matches 5.11, 5.12, 5.13, 5.14, or 5.15.0-5.15.6. Additionally, check if sata_fsl is in use: lsmod | grep sata_fsl. If both conditions are true, your system is vulnerable.

Does Defensia detect CVE-2021-47549?

Yes — Defensia's CVE advisory scanner compares installed kernel package versions against the NVD database. If you are running a vulnerable kernel version on a monitored server, CVE-2021-47549 will appear in your dashboard with remediation steps specific to your Linux distribution.

Related Kernel CVEs

CVE-2024-42256CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: cifs: Fix server re-repick on subrequest retry When a subrequest is marked for needing retry, netfs will call cifs_prepare_write() which will make cifs repick the server for the op before renegotiating credits; it then calls cifs_issue_write() which invokes smb2_async_writev() - which re-repicks the server. If a different server is then selected, this causes the increment of server->in_flight to happen against one record and the decrement to happen against another, leading to misaccounting. Fix this by just removing the repick code in smb2_async_writev(). As this is only called from netfslib-driven code, cifs_prepare_write() should always have been called first, and so server should never be NULL and the preparatory step is repeated in the event that we do a retry. The problem manifests as a warning looking something like: WARNING: CPU: 4 PID: 72896 at fs/smb/client/smb2ops.c:97 smb2_add_credits+0x3f0/0x9e0 [cifs] ... RIP: 0010:smb2_add_credits+0x3f0/0x9e0 [cifs] ... smb2_writev_callback+0x334/0x560 [cifs] cifs_demultiplex_thread+0x77a/0x11b0 [cifs] kthread+0x187/0x1d0 ret_from_fork+0x34/0x60 ret_from_fork_asm+0x1a/0x30 Which may be triggered by a number of different xfstests running against an Azure server in multichannel mode. generic/249 seems the most repeatable, but generic/215, generic/249 and generic/308 may also show it.
CVE-2024-36031CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: keys: Fix overwrite of key expiration on instantiation The expiry time of a key is unconditionally overwritten during instantiation, defaulting to turn it permanent. This causes a problem for DNS resolution as the expiration set by user-space is overwritten to TIME64_MAX, disabling further DNS updates. Fix this by restoring the condition that key_set_expiry is only called when the pre-parser sets a specific expiry.
CVE-2024-38612CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ipv6: sr: fix invalid unregister error path The error path of seg6_init() is wrong in case CONFIG_IPV6_SEG6_LWTUNNEL is not defined. In that case if seg6_hmac_init() fails, the genl_unregister_family() isn't called. This issue exist since commit 46738b1317e1 ("ipv6: sr: add option to control lwtunnel support"), and commit 5559cea2d5aa ("ipv6: sr: fix possible use-after-free and null-ptr-deref") replaced unregister_pernet_subsys() with genl_unregister_family() in this error path.
CVE-2024-38623CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: Use variable length array instead of fixed size Should fix smatch warning: ntfs_set_label() error: __builtin_memcpy() 'uni->name' too small (20 vs 256)
CVE-2021-47548CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ethernet: hisilicon: hns: hns_dsaf_misc: fix a possible array overflow in hns_dsaf_ge_srst_by_port() The if statement: if (port >= DSAF_GE_NUM) return; limits the value of port less than DSAF_GE_NUM (i.e., 8). However, if the value of port is 6 or 7, an array overflow could occur: port_rst_off = dsaf_dev->mac_cb[port]->port_rst_off; because the length of dsaf_dev->mac_cb is DSAF_MAX_PORT_NUM (i.e., 6). To fix this possible array overflow, we first check port and if it is greater than or equal to DSAF_MAX_PORT_NUM, the function returns.

References

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