CVE-2024-49883

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> ext4: aovid use-after-free in ext4_ext_insert_extent()<br /> <br /> As Ojaswin mentioned in Link, in ext4_ext_insert_extent(), if the path is<br /> reallocated in ext4_ext_create_new_leaf(), we&amp;#39;ll use the stale path and<br /> cause UAF. Below is a sample trace with dummy values:<br /> <br /> ext4_ext_insert_extent<br /> path = *ppath = 2000<br /> ext4_ext_create_new_leaf(ppath)<br /> ext4_find_extent(ppath)<br /> path = *ppath = 2000<br /> if (depth &gt; path[0].p_maxdepth)<br /> kfree(path = 2000);<br /> *ppath = path = NULL;<br /> path = kcalloc() = 3000<br /> *ppath = 3000;<br /> return path;<br /> /* here path is still 2000, UAF! */<br /> eh = path[depth].p_hdr<br /> <br /> ==================================================================<br /> BUG: KASAN: slab-use-after-free in ext4_ext_insert_extent+0x26d4/0x3330<br /> Read of size 8 at addr ffff8881027bf7d0 by task kworker/u36:1/179<br /> CPU: 3 UID: 0 PID: 179 Comm: kworker/u6:1 Not tainted 6.11.0-rc2-dirty #866<br /> Call Trace:<br /> <br /> ext4_ext_insert_extent+0x26d4/0x3330<br /> ext4_ext_map_blocks+0xe22/0x2d40<br /> ext4_map_blocks+0x71e/0x1700<br /> ext4_do_writepages+0x1290/0x2800<br /> [...]<br /> <br /> Allocated by task 179:<br /> ext4_find_extent+0x81c/0x1f70<br /> ext4_ext_map_blocks+0x146/0x2d40<br /> ext4_map_blocks+0x71e/0x1700<br /> ext4_do_writepages+0x1290/0x2800<br /> ext4_writepages+0x26d/0x4e0<br /> do_writepages+0x175/0x700<br /> [...]<br /> <br /> Freed by task 179:<br /> kfree+0xcb/0x240<br /> ext4_find_extent+0x7c0/0x1f70<br /> ext4_ext_insert_extent+0xa26/0x3330<br /> ext4_ext_map_blocks+0xe22/0x2d40<br /> ext4_map_blocks+0x71e/0x1700<br /> ext4_do_writepages+0x1290/0x2800<br /> ext4_writepages+0x26d/0x4e0<br /> do_writepages+0x175/0x700<br /> [...]<br /> ==================================================================<br /> <br /> So use *ppath to update the path to avoid the above problem.