CVE-2026-63883

CVE-2026-63883 · serial: qcom_geni: fix kfifo underflow when flush precedes DMA completion IRQ

CVSS 7.3 · Hoch · EPSS 0,2% · Korrektur verfügbar

dpkg-query -W -f='${source:Package} ${binary:Package} ${Version}\n' | awk '$1=="linux"'

dpkg-query -W -f='${source:Package} ${binary:Package} ${Version}\n' | awk '$1=="linux-hwe-edge"'

curl -fsSL https://patchfirst.dev/check.sh | sh

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In 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.

Veröffentlicht

2026-07-19T14:54:56.356Z

Aktualisiert

2026-08-05T12:36:52.126Z

Technologie-Stack: system

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