CVE-2024-53166

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

block, bfq: fix bfqq uaf in bfqlimitdepth()

Set new allocated bfqq to bic or remove freed bfqq from bic are both protected by bfqd->lock, however bfqlimitdepth() is deferencing bfqq from bic without the lock, this can lead to UAF if the io_context is shared by multiple tasks.

For example, test bfq with io_uring can trigger following UAF in v6.6:

================================================================== BUG: KASAN: slab-use-after-free in bfqq_group+0x15/0x50

Call Trace: <TASK> dumpstacklvl+0x47/0x80 printaddressdescription.constprop.0+0x66/0x300 printreport+0x3e/0x70 kasanreport+0xb4/0xf0 bfqqgroup+0x15/0x50 bfqqrequestoverlimit+0x130/0x9a0 bfqlimitdepth+0x1b5/0x480 _blkmqallocrequests+0x2b5/0xa00 blkmqgetnewrequests+0x11d/0x1d0 blkmqsubmitbio+0x286/0xb00 submitbionoacctnocheck+0x331/0x400 _blockwritefullfolio+0x3d0/0x640 writepagecb+0x3b/0xc0 writecachepages+0x254/0x6c0 writecachepages+0x254/0x6c0 dowritepages+0x192/0x310 filemapfdatawritewbc+0x95/0xc0 _filemapfdatawriterange+0x99/0xd0 filemapwriteandwaitrange.part.0+0x4d/0xa0 blkdevreaditer+0xef/0x1e0 ioread+0x1b6/0x8a0 ioissuesqe+0x87/0x300 iowqsubmitwork+0xeb/0x390 ioworkerhandlework+0x24d/0x550 iowqworker+0x27f/0x6c0 retfromfork_asm+0x1b/0x30 </TASK>

Allocated by task 808602: kasansavestack+0x1e/0x40 kasansettrack+0x21/0x30 _kasanslaballoc+0x83/0x90 kmemcacheallocnode+0x1b1/0x6d0 bfqgetqueue+0x138/0xfa0 bfqgetbfqqhandlesplit+0xe3/0x2c0 bfqinitrq+0x196/0xbb0 bfqinsertrequest.isra.0+0xb5/0x480 bfqinsertrequests+0x156/0x180 blkmqinsertrequest+0x15d/0x440 blkmqsubmitbio+0x8a4/0xb00 submitbionoacctnocheck+0x331/0x400 _blkdevdirectIOasync+0x2dd/0x330 blkdevwriteiter+0x39a/0x450 iowrite+0x22a/0x840 ioissuesqe+0x87/0x300 iowqsubmitwork+0xeb/0x390 ioworkerhandlework+0x24d/0x550 iowqworker+0x27f/0x6c0 retfromfork+0x2d/0x50 retfromfork_asm+0x1b/0x30

Freed by task 808589: kasansavestack+0x1e/0x40 kasansettrack+0x21/0x30 kasansavefreeinfo+0x27/0x40 _kasanslabfree+0x126/0x1b0 kmemcachefree+0x10c/0x750 bfqputqueue+0x2dd/0x770 _bfqinsertrequest.isra.0+0x155/0x7a0 bfqinsertrequest.isra.0+0x122/0x480 bfqinsertrequests+0x156/0x180 blkmqdispatchpluglist+0x528/0x7e0 blkmqflushpluglist.part.0+0xe5/0x590 _blkflushplug+0x3b/0x90 blkfinishplug+0x40/0x60 dowritepages+0x19d/0x310 filemapfdatawritewbc+0x95/0xc0 _filemapfdatawriterange+0x99/0xd0 filemapwriteandwaitrange.part.0+0x4d/0xa0 blkdevreaditer+0xef/0x1e0 ioread+0x1b6/0x8a0 ioissuesqe+0x87/0x300 iowqsubmitwork+0xeb/0x390 ioworkerhandlework+0x24d/0x550 iowqworker+0x27f/0x6c0 retfromfork+0x2d/0x50 retfromforkasm+0x1b/0x30

Fix the problem by protecting bictobfqq() with bfqd->lock.