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platform/x86: hp-bioscfg: fix heap OOB read in sk_store() and kek_store()

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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.

Fixes: b2715aa2e1 ("platform/x86: hp-bioscfg: spmobj-attributes")
Cc: stable@vger.kernel.org
Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
Link: https://patch.msgid.link/20260812111829.172273-3-meatuni001@gmail.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
This commit is contained in:
Muhammad Bilal 2026-08-12 16:18:22 +05:00 committed by Ilpo Järvinen
parent dc03f05e41
commit a7508c7959
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GPG Key ID: 59AC4F6153E5CE31
1 changed files with 2 additions and 2 deletions
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4
drivers/platform/x86/hp/hp-bioscfg/spmobj-attributes.c
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@ -238,7 +238,7 @@ static ssize_t sk_store(struct kobject *kobj,
ret = hp_wmi_perform_query(HPWMI_SECUREPLATFORM_SET_SK,
HPWMI_SECUREPLATFORM,
(void *)bioscfg_drv.spm_data.signing_key,
count, 0);
length, 0);
if (!ret) {
bioscfg_drv.spm_data.mechanism = SIGNING_KEY;
@ -274,7 +274,7 @@ static ssize_t kek_store(struct kobject *kobj,
ret = hp_wmi_perform_query(HPWMI_SECUREPLATFORM_SET_KEK,
HPWMI_SECUREPLATFORM,
(void *)bioscfg_drv.spm_data.endorsement_key,
count, 0);
length, 0);
if (!ret) {
bioscfg_drv.spm_data.mechanism = ENDORSEMENT_KEY;