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Linux KernelOperating system · Linux

CVE-2021-47578

MEDIUM · 5.5 CVSS v3.1 Published 2024-06-19
Fix available
A fix is available. Upgrade to 5.10.88 / 5.15.11 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: scsi: scsi_debug: Don't call kcalloc() if size arg is zero If the size arg to kcalloc() is zero, it returns ZERO_SIZE_PTR. Because of that, for a following NULL pointer check to work on the returned pointer, kcalloc() must not be called with the size arg equal to zero. Return early without error before the kcalloc() call if size arg is zero. BUG: KASAN: null-ptr-deref in memcpy include/linux/fortify-string.h:191 [inline] BUG: KASAN: null-ptr-deref in sg_copy_buffer+0x138/0x240 lib/scatterlist.c:974 Write of size 4 at addr 0000000000000010 by task syz-executor.1/22789 CPU: 1 PID: 22789 Comm: syz-executor.1 Not tainted 5.15.0-syzk #1 Hardware name: Red Hat KVM, BIOS 1.13.0-2 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x89/0xb5 lib/dump_stack.c:106 __kasan_report mm/kasan/report.c:446 [inline] kasan_report.cold.14+0x112/0x117 mm/kasan/report.c:459 check_region_inline mm/kasan/generic.c:183 [inline] kasan_check_range+0x1a3/0x210 mm/kasan/generic.c:189 memcpy+0x3b/0x60 mm/kasan/shadow.c:66 memcpy include/linux/fortify-string.h:191 [inline] sg_copy_buffer+0x138/0x240 lib/scatterlist.c:974 do_dout_fetch drivers/scsi/scsi_debug.c:2954 [inline] do_dout_fetch drivers/scsi/scsi_debug.c:2946 [inline] resp_verify+0x49e/0x930 drivers/scsi/scsi_debug.c:4276 schedule_resp+0x4d8/0x1a70 drivers/scsi/scsi_debug.c:5478 scsi_debug_queuecommand+0x8c9/0x1ec0 drivers/scsi/scsi_debug.c:7533 scsi_dispatch_cmd drivers/scsi/scsi_lib.c:1520 [inline] scsi_queue_rq+0x16b0/0x2d40 drivers/scsi/scsi_lib.c:1699 blk_mq_dispatch_rq_list+0xb9b/0x2700 block/blk-mq.c:1639 __blk_mq_sched_dispatch_requests+0x28f/0x590 block/blk-mq-sched.c:325 blk_mq_sched_dispatch_requests+0x105/0x190 block/blk-mq-sched.c:358 __blk_mq_run_hw_queue+0xe5/0x150 block/blk-mq.c:1761 __blk_mq_delay_run_hw_queue+0x4f8/0x5c0 block/blk-mq.c:1838 blk_mq_run_hw_queue+0x18d/0x350 block/blk-mq.c:1891 blk_mq_sched_insert_request+0x3db/0x4e0 block/blk-mq-sched.c:474 blk_execute_rq_nowait+0x16b/0x1c0 block/blk-exec.c:62 blk_execute_rq+0xdb/0x360 block/blk-exec.c:102 sg_scsi_ioctl drivers/scsi/scsi_ioctl.c:621 [inline] scsi_ioctl+0x8bb/0x15c0 drivers/scsi/scsi_ioctl.c:930 sg_ioctl_common+0x172d/0x2710 drivers/scsi/sg.c:1112 sg_ioctl+0xa2/0x180 drivers/scsi/sg.c:1165 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __x64_sys_ioctl+0x19d/0x220 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-476

The code follows a pointer that is null, crashing the process. An attacker who can reliably trigger it turns the crash into a denial of service. The fix is checking for null before use and handling the failure path gracefully.

General guidance for the null pointer dereference class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:< 5.10.88>= 5.11, < 5.15.11

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.10.88 / 5.15.11 or later
Fixed in 5.10.885.15.11
Vendor patch git.kernel.org →
Recommended fix High confidence

Linux kernel 5.10.88+ (for 5.10.y branch) or 5.15.11+ (for 5.11.y-5.15.y branches), or any version >= 5.16

  1. Identify current kernel version using `uname -r`
  2. Determine which upgrade path is appropriate based on your current kernel branch (5.10.x or 5.11.x-5.15.x)
  3. For systems running kernel < 5.10.88: upgrade to kernel 5.10.88 or later (e.g., 5.10.88, 5.10.x stable)
  4. For systems running kernel >= 5.11 and < 5.15.11: upgrade to kernel 5.15.11 or later (e.g., 5.15.11, 5.15.x stable)
  5. Alternatively, upgrade to any kernel version >= 5.16 which contains the fix
  6. Apply the kernel upgrade using your distribution's package manager (e.g., `apt-get update && apt-get install linux-image-*` for Debian/Ubuntu, or `yum update kernel` for RHEL/CentOS)
  7. Reboot the system to load the fixed kernel
Caveat Kernel upgrades may require system reboot and could introduce compatibility issues with custom modules or specific hardware configurations; test in non-production environment first

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $2,850. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-47578 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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