serial: qcom_geni: fix kfifo underflow when flush precedes DMA completion IRQ

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-63883
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 16:17:05 UTC
Updated2026-07-20 15:16:53 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: serial: qcom_geni: fix kfifo underflow when flush precedes DMA completion IRQ When uart_flush_buffer() runs before the DMA completion IRQ is delivered, the following race can occur (all steps serialized by uart_port_lock): 1. DMA starts: tx_remaining = N, kfifo contains N bytes 2. DMA completes in hardware; IRQ is pending but not yet delivered 3. uart_flush_buffer() acquires the port lock and calls kfifo_reset(), making kfifo_len() = 0 while tx_remaining remains N 4. uart_flush_buffer() releases the port lock 5. DMA IRQ fires; handle_tx_dma() acquires the port lock and calls uart_xmit_advance(uport, tx_remaining) on an empty kfifo uart_xmit_advance() increments kfifo->out by tx_remaining. Since kfifo_reset() already set both in and out to 0, out wraps past in, causing kfifo_len() to return UART_XMIT_SIZE - tx_remaining. The next start_tx_dma() call then submits a DMA transfer of stale buffer data. Fix this by snapshotting kfifo_len() at the start of handle_tx_dma() and skipping uart_xmit_advance() when fifo_len < tx_remaining, which indicates the kfifo was reset by a preceding flush.

Risk And Classification

Primary CVSS: v3.1 7.3 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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

EPSS: 0.002000000 probability, percentile 0.100190000 (date 2026-07-20)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.3HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L
3.1CNADECLARED7.3HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
Low

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 2aaa43c7077833301c237684cd7bc9ae5e3dec95 c91ea13375f70f6271a0183445e34e83b8f4d8f7 git Not specified
CNA Linux Linux affected 2aaa43c7077833301c237684cd7bc9ae5e3dec95 b1159dce10b38eb795e4c96cdc4d34b83cec81c5 git Not specified
CNA Linux Linux affected 2aaa43c7077833301c237684cd7bc9ae5e3dec95 654f45a8569f3cd6ff20bd724a18e0cce65893ba git Not specified
CNA Linux Linux affected 2aaa43c7077833301c237684cd7bc9ae5e3dec95 0d2c41a8b00934ddf8a7c1b4cf72dffa1e629c46 git Not specified
CNA Linux Linux affected 2aaa43c7077833301c237684cd7bc9ae5e3dec95 452d6fa37ae9b021f4f6d397dbae077f7296f6f4 git Not specified
CNA Linux Linux affected 6.3 Not specified
CNA Linux Linux unaffected 6.3 semver Not specified
CNA Linux Linux unaffected 6.6.143 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.93 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.35 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.12 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/452d6fa37ae9b021f4f6d397dbae077f7296f6f4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b1159dce10b38eb795e4c96cdc4d34b83cec81c5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/654f45a8569f3cd6ff20bd724a18e0cce65893ba 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0d2c41a8b00934ddf8a7c1b4cf72dffa1e629c46 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c91ea13375f70f6271a0183445e34e83b8f4d8f7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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