CVE-2026-74276 (GCVE-0-2026-74276)
Vulnerability from cvelistv5
Published
2026-08-15 05:57
Modified
2026-08-17 05:16
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
spi: xilinx: use FIFO occupancy register to determine buffer size
The method the driver uses to determine the size of the FIFO has a
problem. What it currently does is this:
It stops the SPI hardware and writes to the TX FIFO register until TX
FIFO FULL asserts in the status register. But the hardware does not only
have the FIFO, it also has a shift register which can hold a byte. This
can be seen, when writing a byte to the FIFO (while the SPI hardware is
stopped,) the TX FIFO EMPTY is still empty. So, if we have a FIFO size
of 16 for example, the current method returns a 17.
This is a problem, at least when using the driver in irq mode. The same
size determined for the TX FIFO is also assumed for the RX FIFO. When a
SPI transaction wants to write the amount of the FIFO size or more
bytes, the following happens, for example with 16 bytes FIFO size:
The driver stops the SPI hardware and writes 17 bytes to the TX FIFO and
starts the SPI hardware and goes sleep.
The hardware then shifts out 17 bytes (FIFO + shift register) and
simultaneously reads bytes into the RX FIFO, but it only has 16 places,
so it looses one byte. Then TX FIFO empty asserts, wakes the driver
again, which has a fast path and reads 16 bytes from the RX FIFO, but
before reading the last 17th byte (which is lost) it does this:
sr = xspi->read_fn(xspi->regs + XSPI_SR_OFFSET);
if (!(sr & XSPI_SR_RX_EMPTY_MASK)) {
xilinx_spi_rx(xspi);
rx_words--;
}
It reads the status register and checks if the RX FIFO is not empty.
But it is empty in our case. So this check spins in a while loop
forever locking the driver.
This patch fixes the logic to determine the FIFO size.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 4c9a761402d780b86b9b068aba4ef8e29ed15e99 Version: 4c9a761402d780b86b9b068aba4ef8e29ed15e99 Version: 4c9a761402d780b86b9b068aba4ef8e29ed15e99 Version: 4c9a761402d780b86b9b068aba4ef8e29ed15e99 Version: 4c9a761402d780b86b9b068aba4ef8e29ed15e99 Version: 4c9a761402d780b86b9b068aba4ef8e29ed15e99 Version: 4c9a761402d780b86b9b068aba4ef8e29ed15e99 Version: 4c9a761402d780b86b9b068aba4ef8e29ed15e99 |
||
{
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nspi: xilinx: use FIFO occupancy register to determine buffer size\n\nThe method the driver uses to determine the size of the FIFO has a\nproblem. What it currently does is this:\nIt stops the SPI hardware and writes to the TX FIFO register until TX\nFIFO FULL asserts in the status register. But the hardware does not only\nhave the FIFO, it also has a shift register which can hold a byte. This\ncan be seen, when writing a byte to the FIFO (while the SPI hardware is\nstopped,) the TX FIFO EMPTY is still empty. So, if we have a FIFO size\nof 16 for example, the current method returns a 17.\nThis is a problem, at least when using the driver in irq mode. The same\nsize determined for the TX FIFO is also assumed for the RX FIFO. When a\nSPI transaction wants to write the amount of the FIFO size or more\nbytes, the following happens, for example with 16 bytes FIFO size:\nThe driver stops the SPI hardware and writes 17 bytes to the TX FIFO and\nstarts the SPI hardware and goes sleep.\nThe hardware then shifts out 17 bytes (FIFO + shift register) and\nsimultaneously reads bytes into the RX FIFO, but it only has 16 places,\nso it looses one byte. Then TX FIFO empty asserts, wakes the driver\nagain, which has a fast path and reads 16 bytes from the RX FIFO, but\nbefore reading the last 17th byte (which is lost) it does this:\n\n\tsr = xspi-\u003eread_fn(xspi-\u003eregs + XSPI_SR_OFFSET);\n\tif (!(sr \u0026 XSPI_SR_RX_EMPTY_MASK)) {\n\t\txilinx_spi_rx(xspi);\n\t\trx_words--;\n\t}\n\nIt reads the status register and checks if the RX FIFO is not empty.\nBut it is empty in our case. So this check spins in a while loop\nforever locking the driver.\n\nThis patch fixes the logic to determine the FIFO size."
}
],
"providerMetadata": {
"dateUpdated": "2026-08-17T05:16:20.426Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/4ee65558a7fda463222f5edc631b6d7862218725"
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{
"url": "https://git.kernel.org/stable/c/e98f589d54068dfcc7da42d9b730e47b84e2991a"
},
{
"url": "https://git.kernel.org/stable/c/1fc6a6c0cc7796b0c1cf4eec3f0720f422f09273"
},
{
"url": "https://git.kernel.org/stable/c/dfab0d4698a642bab9b895e2e6d240838cfe2cc6"
},
{
"url": "https://git.kernel.org/stable/c/d7ccd8736b67550eca746ed7fa39a36016ff114b"
},
{
"url": "https://git.kernel.org/stable/c/1c9246a199e19b2fd36e94feed60e55f27103a4f"
},
{
"url": "https://git.kernel.org/stable/c/d1944b71c18e7494756bff1a6f80c25be99eaecb"
},
{
"url": "https://git.kernel.org/stable/c/47f3b5365536e8c38f264824ab15fdb74454e066"
}
],
"title": "spi: xilinx: use FIFO occupancy register to determine buffer size",
"x_generator": {
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}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74276",
"datePublished": "2026-08-15T05:57:48.115Z",
"dateReserved": "2026-08-15T05:44:03.880Z",
"dateUpdated": "2026-08-17T05:16:20.426Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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