In the Linux kernel, the following vulnerability has been resolved:
platform/x86: hp-bioscfg: fix heap OOB read in sk_store() and kek_store()
sk_store() and kek_store() strip a trailing newline from the sysfs
write before allocating the key buffer:
length = count;
if (buf[length – 1] == ‘n’)
length–;
bioscfg_drv.spm_data.signing_key = kmemdup(buf, length, GFP_KERNEL);
but then pass the original “count” (not “length”) as the copy size to
hp_wmi_perform_query(), which memcpy()s that many bytes out of the
“length”-sized allocation, reading one byte past it whenever the write
ends in a newline, the normal case for a shell “echo” into sysfs.
KASAN confirms this directly:
BUG: KASAN: slab-out-of-bounds in hp_wmi_perform_query+0x1e9/0x460 [hp_bioscfg]
Read of size 28 at addr ffff88813c8e2b80 by task python3/16022
…
sk_store+0xa7/0x240 [hp_bioscfg]
kernfs_fop_write_iter+0x3e1/0x5d0
…
The buggy address is located 0 bytes inside of
allocated 27-byte region [ffff88813c8e2b80, ffff88813c8e2b9b)
Reproduced identically for kek_store, and at multiple write sizes
(28, 57, 201 bytes), each time reading exactly one byte past a
kmemdup() allocation one byte smaller than the write.
Fix by passing “length” instead of “count” to hp_wmi_perform_query()
in both functions.
