In the Linux kernel, the following vulnerability has been resolved:
ext4: aovid use-after-free in ext4extinsert_extent()
As Ojaswin mentioned in Link, in ext4extinsertextent(), if the path is reallocated in ext4extcreatenew_leaf(), we'll use the stale path and cause UAF. Below is a sample trace with dummy values:
ext4extinsertextent path = *ppath = 2000 ext4extcreatenewleaf(ppath) ext4findextent(ppath) path = *ppath = 2000 if (depth > path[0].pmaxdepth) 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 ext4extinsertextent+0x26d4/0x3330 Read of size 8 at addr ffff8881027bf7d0 by task kworker/u36:1/179 CPU: 3 UID: 0 PID: 179 Comm: kworker/u6:1 Not tainted 6.11.0-rc2-dirty #866 Call Trace: <TASK> ext4extinsertextent+0x26d4/0x3330 ext4extmapblocks+0xe22/0x2d40 ext4mapblocks+0x71e/0x1700 ext4do_writepages+0x1290/0x2800 [...]
Allocated by task 179: ext4findextent+0x81c/0x1f70 ext4extmapblocks+0x146/0x2d40 ext4mapblocks+0x71e/0x1700 ext4dowritepages+0x1290/0x2800 ext4writepages+0x26d/0x4e0 do_writepages+0x175/0x700 [...]
Freed by task 179: kfree+0xcb/0x240 ext4findextent+0x7c0/0x1f70 ext4extinsertextent+0xa26/0x3330 ext4extmapblocks+0xe22/0x2d40 ext4mapblocks+0x71e/0x1700 ext4dowritepages+0x1290/0x2800 ext4writepages+0x26d/0x4e0 dowritepages+0x175/0x700
So use *ppath to update the path to avoid the above problem.
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"target": {
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},
"digest": {
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},
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},
{
"deprecated": false,
"target": {
"file": "fs/ext4/extents.c",
"function": "ext4_ext_insert_extent"
},
"digest": {
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"length": 4782.0
},
"id": "CVE-2024-49883-1bf4afe6",
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},
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"target": {
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{
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"target": {
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"function": "ext4_ext_insert_extent"
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"digest": {
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"id": "CVE-2024-49883-25137e7a",
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"source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@975ca06f3fd154c5f7742083e7b2574c57d1c0c3",
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"id": "CVE-2024-49883-2b881e64",
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},
{
"deprecated": false,
"target": {
"file": "fs/ext4/extents.c",
"function": "ext4_ext_insert_extent"
},
"digest": {
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