In the Linux kernel, the following vulnerability has been resolved: netfs: Fix write streaming disablement if fd open O_RDWR In… (CVE-2026-64158)
In the Linux kernel, the following vulnerability has been resolved: netfs: Fix write streaming disablement if fd open O_RDWR In netfs_perform_write(), "write streaming" (the caching of dirty data in dirty but !uptodate folios) is performed to avoid the need to read data that is just going to get immediately overwritten. However, this is/will be disabled in three circumstances: if the fd is open O_RDWR, if fscache is in use (as we need to round out the blocks for DIO) or if content encryption is enabled (again for rounding out purposes). The idea behind disabling it if the fd is open O_RDWR is that we'd need to flush the write-streaming page before we could read the data, particularly through mmap. But netfs now fills in the gaps if ->read_folio() is called on the page, so that is unnecessary. Further, this doesn't actually work if a separate fd is open for reading. Fix this by removing the check for O_RDWR, thereby allowing streaming writes even when we might read. This caused a number of problems with the generic/522 xfstest, but those are now fixed.
AI Analysis
Technical Summary
The Linux kernel netfs subsystem performed write streaming to cache dirty data and avoid unnecessary reads. Previously, write streaming was disabled if the file descriptor was opened with O_RDWR, due to concerns about flushing pages before reads, especially via mmap. However, this disabling was unnecessary because netfs handles read gaps internally, and it did not work correctly if a separate file descriptor was open for reading. The vulnerability was fixed by removing the check that disabled write streaming for O_RDWR, restoring proper streaming behavior and fixing related filesystem test failures.
Potential Impact
The vulnerability caused improper disabling of write streaming in netfs when a file descriptor was opened with O_RDWR, potentially leading to data consistency and performance issues. The fix restores correct write streaming behavior, improving filesystem stability and correctness. There is no indication of direct security exploitation or data compromise from this issue.
Mitigation Recommendations
A fix has been applied in the Linux kernel to remove the disabling of write streaming for O_RDWR file descriptors in netfs. Users should update to the fixed kernel version once available. No additional mitigation actions are indicated.
In the Linux kernel, the following vulnerability has been resolved: netfs: Fix write streaming disablement if fd open O_RDWR In… (CVE-2026-64158)
Description
In the Linux kernel, the following vulnerability has been resolved: netfs: Fix write streaming disablement if fd open O_RDWR In netfs_perform_write(), "write streaming" (the caching of dirty data in dirty but !uptodate folios) is performed to avoid the need to read data that is just going to get immediately overwritten. However, this is/will be disabled in three circumstances: if the fd is open O_RDWR, if fscache is in use (as we need to round out the blocks for DIO) or if content encryption is enabled (again for rounding out purposes). The idea behind disabling it if the fd is open O_RDWR is that we'd need to flush the write-streaming page before we could read the data, particularly through mmap. But netfs now fills in the gaps if ->read_folio() is called on the page, so that is unnecessary. Further, this doesn't actually work if a separate fd is open for reading. Fix this by removing the check for O_RDWR, thereby allowing streaming writes even when we might read. This caused a number of problems with the generic/522 xfstest, but those are now fixed.
CVSS v3.1
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Linux kernel netfs subsystem performed write streaming to cache dirty data and avoid unnecessary reads. Previously, write streaming was disabled if the file descriptor was opened with O_RDWR, due to concerns about flushing pages before reads, especially via mmap. However, this disabling was unnecessary because netfs handles read gaps internally, and it did not work correctly if a separate file descriptor was open for reading. The vulnerability was fixed by removing the check that disabled write streaming for O_RDWR, restoring proper streaming behavior and fixing related filesystem test failures.
Potential Impact
The vulnerability caused improper disabling of write streaming in netfs when a file descriptor was opened with O_RDWR, potentially leading to data consistency and performance issues. The fix restores correct write streaming behavior, improving filesystem stability and correctness. There is no indication of direct security exploitation or data compromise from this issue.
Mitigation Recommendations
A fix has been applied in the Linux kernel to remove the disabling of write streaming for O_RDWR file descriptors in netfs. Users should update to the fixed kernel version once available. No additional mitigation actions are indicated.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-74f7-4jjx-chgc
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-64158"]
- Ecosystems
- []
- Database Specific Severity
- null
- Cvss Version
- null
Threat ID: 6a5d27a82a4a8d598912a583
Added to database: 07/19/2026, 19:38:16 UTC
Last enriched: 07/19/2026, 19:42:06 UTC
Last updated: 07/20/2026, 19:41:21 UTC
Views: 12
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