Bug 2393186 (CVE-2025-38685) - CVE-2025-38685 kernel: fbdev: Fix vmalloc out-of-bounds write in fast_imageblit
Summary: CVE-2025-38685 kernel: fbdev: Fix vmalloc out-of-bounds write in fast_imageblit
Keywords:
Status: NEW
Alias: CVE-2025-38685
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2025-09-04 16:03 UTC by OSIDB Bzimport
Modified: 2025-09-06 00:40 UTC (History)
0 users

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:


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Description OSIDB Bzimport 2025-09-04 16:03:43 UTC
In the Linux kernel, the following vulnerability has been resolved:

fbdev: Fix vmalloc out-of-bounds write in fast_imageblit

This issue triggers when a userspace program does an ioctl
FBIOPUT_CON2FBMAP by passing console number and frame buffer number.
Ideally this maps console to frame buffer and updates the screen if
console is visible.

As part of mapping it has to do resize of console according to frame
buffer info. if this resize fails and returns from vc_do_resize() and
continues further. At this point console and new frame buffer are mapped
and sets display vars. Despite failure still it continue to proceed
updating the screen at later stages where vc_data is related to previous
frame buffer and frame buffer info and display vars are mapped to new
frame buffer and eventully leading to out-of-bounds write in
fast_imageblit(). This bheviour is excepted only when fg_console is
equal to requested console which is a visible console and updates screen
with invalid struct references in fbcon_putcs().


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