CVE-2026-90190
In the Linux kernel, the following vulnerability has been resolved: null_blk: use DEFINE_MUTEX for the file-scope mutex In null_init(), mutex_init(&lock) currently happens after configfs_register_subsystem(), which exposes the nullb subsystem to userspace. A racing mkdir() into /sys/kernel/config/nullb/ can reach null_find_dev_by_name() -> mutex_lock(&lock) before the mutex is initialized, trigger warning: [ 123.137788] DEBUG_LOCKS_WARN_ON(lock->magic != lock) [ 123.137796] WARNING: kernel/locking/mutex.c:159 at mutex_lock+0x171/0x1c0, CPU#13: mkdir/1301 [ 123.140090] Modules linked in: null_blk(+) nft_fib_inet nft_fib_ipv4 ...... [ 123.154926] Call Trace: [ 123.155172] <TASK> [ 123.155419] ? __pfx_mutex_lock+0x10/0x10 [ 123.156181] ? __pfx__raw_spin_lock+0x10/0x10 [ 123.156571] nullb_group_make_group+0x20/0x100 [null_blk] [ 123.157011] configfs_mkdir+0x47b/0xc70 [ 123.157337] ? __pfx_configfs_mkdir+0x10/0x10 [ 123.157719] ? may_create_dentry+0x242/0x2e0 [ 123.158061] vfs_mkdir+0x2a9/0x6c0 [ 123.158352] filename_mkdirat+0x3dc/0x500 [ 123.158710] ? __pfx_filename_mkdirat+0x10/0x10 [ 123.159070] ? strncpy_from_user+0x3a/0x1d0 [ 123.159413] __x64_sys_mkdir+0x6b/0x90 [ 123.159760] do_syscall_64+0xea/0x600 Replace the runtime mutex_init(&lock) with a static DEFINE_MUTEX(lock) declaration to fix this issue.
Executive briefing
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Evidence confidence: Not assessed Evidence-derived, not an exploitability verdict
Severity & attack characteristics
CVSS vector:Not supplied
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Technical explanation & impact
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Affected products and versions
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Remediation & validation
- Identify exposure by comparing the affected product and version ranges with your asset inventory, SBOM and externally exposed services.
- Review the linked vendor security advisory or patch notes. Upgrade to a vendor-confirmed fixed release; do not infer a fixed version from the CVE description.
- Until patched, consider restricting network access or disabling the affected feature where operationally safe. These are temporary controls, not a substitute for a vendor fix.
- Validate the remediation with a version check and vulnerability rescan, then retain change evidence.
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Vendor advisories, patches & exploit references
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