ocfs2: avoid moving extents to occupied clusters

Overview

In the Linux kernel, the following vulnerability has been resolved:

ocfs2: avoid moving extents to occupied clusters

For non-auto OCFS2_IOC_MOVE_EXT operations, userspace supplies a physical me_goal. ocfs2_move_extent() initializes new_phys_cpos from that goal and expects ocfs2_probe_alloc_group() to replace it with a free run in the target block group.

The probe currently leaves *phys_cpos unchanged if the scan reaches the end of the group without finding a free run. An occupied goal at the last bit can therefore survive the probe and be passed to __ocfs2_move_extent(), which copies file data into a cluster still owned by another inode before the bitmap is updated.

When the probe does find a free run, it also subtracts move_len from the ending bit. The start of an N-bit run ending at i is i - N + 1, so the current calculation can report the bit immediately before the free run.

Clear *phys_cpos before scanning and use the correct free-run start. Callers already treat a zero result as -ENOSPC, so failed probes no longer continue with an occupied caller-controlled goal.

Affected

• Linux >= e6b5859cccfa0fec02f3c5b1069481efc7186f47 < 3112afebf2a76e522fbaabcbb0c47aafbdc35932
• Linux >= e6b5859cccfa0fec02f3c5b1069481efc7186f47 < 35486b291b8fbde6c4d0b1c79e565c6260d3329d
• Linux >= e6b5859cccfa0fec02f3c5b1069481efc7186f47 < 19f7b04924b20b81dabbeed19d5542792ba5b6d6
• Linux >= e6b5859cccfa0fec02f3c5b1069481efc7186f47 < e281d892ce5870a50fdc718cb3bfc3dd5b62c728
• Linux >= e6b5859cccfa0fec02f3c5b1069481efc7186f47 < 0d0c5c17b18bdbc592ac26ab4d1de7e3dbf9be1e
• Linux >= e6b5859cccfa0fec02f3c5b1069481efc7186f47 < d5d5a21fb33cd9b963aea99da81e4dacd452cd95
• Linux >= e6b5859cccfa0fec02f3c5b1069481efc7186f47 < 4d1953d3aeb4a7f6623083e1839068ee1c157db2
• Linux >= e6b5859cccfa0fec02f3c5b1069481efc7186f47 < 22920541c35a9f23f219038ba5874c843a7c4419
• Linux 3.0

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.