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

mm/vmalloc: fix data race in show_numa_info()

The following data-race was found in show_numa_info():

================================================================== BUG: KCSAN: data-race in vmalloc_info_show / vmalloc_info_show

read to 0xffff88800971fe30 of 4 bytes by task 8289 on cpu 0: show_numa_info mm/vmalloc.c:4936 [inline] vmalloc_info_show+0x5a8/0x7e0 mm/vmalloc.c:5016 seq_read_iter+0x373/0xb40 fs/seq_file.c:230 proc_reg_read_iter+0x11e/0x170 fs/proc/inode.c:299 ….

write to 0xffff88800971fe30 of 4 bytes by task 8287 on cpu 1: show_numa_info mm/vmalloc.c:4934 [inline] vmalloc_info_show+0x38f/0x7e0 mm/vmalloc.c:5016 seq_read_iter+0x373/0xb40 fs/seq_file.c:230 proc_reg_read_iter+0x11e/0x170 fs/proc/inode.c:299 ….

value changed: 0x0000008f -> 0x00000000

According to this report,there is a read/write data-race because m->private is accessible to multiple CPUs. To fix this, instead of allocating the heap in proc_vmalloc_init() and passing the heap address to m->private, vmalloc_info_show() should allocate the heap.

Affected Software

References

• https://git.kernel.org/stable/c/5c5f0468d172ddec2e333d738d2a1f85402cf0bc
• https://git.kernel.org/stable/c/5c966f447a584ece3c70395898231aeb56256ee7
• https://git.kernel.org/stable/c/ead91de35d9cd5c4f80ec51e6020f342079170af