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CVE-2024-49883

Description

In the Linux kernel, the following vulnerability has been resolved:ext4: aovid use-after-free in ext4_ext_insert_extent()As Ojaswin mentioned in Link, in ext4_ext_insert_extent(), if the path isreallocated in ext4_ext_create_new_leaf(), we'll use the stale path andcause UAF. Below is a sample trace with dummy values:ext4_ext_insert_extent path = *ppath = 2000 ext4_ext_create_new_leaf(ppath) ext4_find_extent(ppath) path = *ppath = 2000 if (depth > path[0].p_maxdepth) kfree(path = 2000); *ppath = path = NULL; path = kcalloc() = 3000 *ppath = 3000; return path; /* here path is still 2000, UAF! */ eh = path[depth].p_hdr==================================================================BUG: KASAN: slab-use-after-free in ext4_ext_insert_extent+0x26d4/0x3330Read of size 8 at addr ffff8881027bf7d0 by task kworker/u36:1/179CPU: 3 UID: 0 PID: 179 Comm: kworker/u6:1 Not tainted 6.11.0-rc2-dirty #866Call Trace: ext4_ext_insert_extent+0x26d4/0x3330 ext4_ext_map_blocks+0xe22/0x2d40 ext4_map_blocks+0x71e/0x1700 ext4_do_writepages+0x1290/0x2800[...]Allocated by task 179: ext4_find_extent+0x81c/0x1f70 ext4_ext_map_blocks+0x146/0x2d40 ext4_map_blocks+0x71e/0x1700 ext4_do_writepages+0x1290/0x2800 ext4_writepages+0x26d/0x4e0 do_writepages+0x175/0x700[...]Freed by task 179: kfree+0xcb/0x240 ext4_find_extent+0x7c0/0x1f70 ext4_ext_insert_extent+0xa26/0x3330 ext4_ext_map_blocks+0xe22/0x2d40 ext4_map_blocks+0x71e/0x1700 ext4_do_writepages+0x1290/0x2800 ext4_writepages+0x26d/0x4e0 do_writepages+0x175/0x700[...]==================================================================So use *ppath to update the path to avoid the above problem.

POC

Reference

No PoCs from references.

Github

- https://github.com/w4zu/Debian_security