Linux vulnerability

What happened

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().

Affected versions

Linux: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 through before 078e62bffca4b7e72e8f3550eb063ab981c36c7a (git); 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 through before 4c4d7ddaf1d43780b106bedc692679f965dc5a3a (git); 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 through before 27b118aebdd84161c8ff5ce49d9d536f2af10754 (git); 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 through before ed9b8e5016230868c8d813d9179523f729fec8c6 (git); 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 through before 56701bf9eeb63219e378cb7fcbd066ea4eaeeb50 (git); 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 through before cfec17721265e72e50cc69c6004fe3475cd38df2 (git); 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 through before af0db3c1f898144846d4c172531a199bb3ca375d (git); 2.6.12; before V5.0 (custom); V3.1.5 through before * (custom) Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.