high CVSS 7.8

CVE-2021-47497·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: nvmem: Fix shift-out-of-bound (UBSAN) with byte size cells If a cell has 'nbits' equal to a multiple of BITS_PER_BYTE the logic *p &= GENMASK((cell->nbits%BITS_PER_BYTE) - 1, 0); will become undefined behavior because nbits modulo BITS_PER_BYTE is 0, and we subtract one from that making a large number that is then shifted more than the number of bits that fit into an unsigned long. UBSAN reports this problem: UBSAN: shift-out-of-bounds in drivers/nvmem/core.c:1386:8 shift exponent 64 is too large for 64-bit type 'unsigned long' CPU: 6 PID: 7 Comm: kworker/u16:0 Not tainted 5.15.0-rc3+ #9 Hardware name: Google Lazor (rev3+) with KB Backlight (DT) Workqueue: events_unbound deferred_probe_work_func Call trace: dump_backtrace+0x0/0x170 show_stack+0x24/0x30 dump_stack_lvl+0x64/0x7c dump_stack+0x18/0x38 ubsan_epilogue+0x10/0x54 __ubsan_handle_shift_out_of_bounds+0x180/0x194 __nvmem_cell_read+0x1ec/0x21c nvmem_cell_read+0x58/0x94 nvmem_cell_read_variable_common+0x4c/0xb0 nvmem_cell_read_variable_le_u32+0x40/0x100 a6xx_gpu_init+0x170/0x2f4 adreno_bind+0x174/0x284 component_bind_all+0xf0/0x264 msm_drm_bind+0x1d8/0x7a0 try_to_bring_up_master+0x164/0x1ac __component_add+0xbc/0x13c component_add+0x20/0x2c dp_display_probe+0x340/0x384 platform_probe+0xc0/0x100 really_probe+0x110/0x304 __driver_probe_device+0xb8/0x120 driver_probe_device+0x4c/0xfc __device_attach_driver+0xb0/0x128 bus_for_each_drv+0x90/0xdc __device_attach+0xc8/0x174 device_initial_probe+0x20/0x2c bus_probe_device+0x40/0xa4 deferred_probe_work_func+0x7c/0xb8 process_one_work+0x128/0x21c process_scheduled_works+0x40/0x54 worker_thread+0x1ec/0x2a8 kthread+0x138/0x158 ret_from_fork+0x10/0x20 Fix it by making sure there are any bits to mask out.

Severity
high
Software
Kernel
Fixed in
5.14.14
Published
2024-05-22

Affected versions

From: 5.11

Until: 5.14.14

Fixed in: 5.14.14

How to fix this CVE

Update your Linux kernel to version 5.14.14 or later to resolve a shift-out-of-bounds undefined behavior in the nvmem core driver. This vulnerability occurs when reading nvmem cells with a bit size that is a multiple of 8, causing improper bit masking operations. Apply the kernel update immediately as this affects memory access operations that could lead to system instability or information disclosure.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your kernel version with `uname -r` and compare against 5.14.14 (vulnerable if running 5.11.x through 5.14.13)
  2. Step 2: Verify nvmem devices are present on the system with `ls -la /sys/bus/nvmem/devices/` to confirm the vulnerable driver is loaded
  3. Step 3: Search kernel logs for UBSAN shift-out-of-bounds errors with `dmesg | grep -i 'shift-out-of-bounds\|nvmem'` or `journalctl -b | grep -i 'shift-out-of-bounds'`
  4. Step 4: After patching, confirm the new kernel version with `uname -r` and verify it returns 5.14.14 or later

FAQ

What is CVE-2021-47497?

CVE-2021-47497 is a kernel vulnerability in the nvmem (non-volatile memory) driver where a modulo operation could produce zero, leading to an out-of-bounds bit shift when the driver attempts to mask cell data. This triggers undefined behavior detected by UBSAN and could cause kernel panics or information leaks.

Is CVE-2021-47497 being actively exploited?

No, CVE-2021-47497 is not documented as actively exploited in the wild or included in the CISA Known Exploited Vulnerabilities catalog. Public exploit code is not available.

What versions of Kernel are affected by CVE-2021-47497?

Linux kernel versions 5.11 through 5.14.13 are vulnerable. Version 5.14.14 and later include the fix.

How do I check if my server is vulnerable to CVE-2021-47497?

Run `uname -r` to get your kernel version. If it shows 5.11.x, 5.12.x, 5.13.x, or 5.14.0 through 5.14.13, your system is vulnerable and requires a kernel update.

Does Defensia detect CVE-2021-47497?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Linux kernel is installed on a monitored server, CVE-2021-47497 will appear in your dashboard with remediation steps.

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CVE-2024-38541CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: of: module: add buffer overflow check in of_modalias() In of_modalias(), if the buffer happens to be too small even for the 1st snprintf() call, the len parameter will become negative and str parameter (if not NULL initially) will point beyond the buffer's end. Add the buffer overflow check after the 1st snprintf() call and fix such check after the strlen() call (accounting for the terminating NUL char).

References

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