CVE-2026-43380: hwmon: (pmbus/q54sj108a2) fix stack overflow in debugfs read

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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

hwmon: (pmbus/q54sj108a2) fix stack overflow in debugfs read

The q54sj108a2_debugfs_read function suffers from a stack buffer overflow
due to incorrect arguments passed to bin2hex(). The function currently
passes 'data' as the destination and 'data_char' as the source.

Because bin2hex() converts each input byte into two hex characters, a
32-byte block read results in 64 bytes of output. Since 'data' is only
34 bytes (I2C_SMBUS_BLOCK_MAX + 2), this writes 30 bytes past the end
of the buffer onto the stack.

Additionally, the arguments were swapped: it was reading from the
zero-initialized 'data_char' and writing to 'data', resulting in
all-zero output regardless of the actual I2C read.

Fix this by:
1. Expanding 'data_char' to 66 bytes to safely hold the hex output.
2. Correcting the bin2hex() argument order and using the actual read count.
3. Using a pointer to select the correct output buffer for the final
   simple_read_from_buffer call.

The Linux kernel CVE team has assigned CVE-2026-43380 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.11 with commit d014538aa38561cd24c5eb228223585f26c5ec71 and fixed in 5.15.203 with commit a0fc1b9c738fba231f190ab960c83202722efee5
	Issue introduced in 5.11 with commit d014538aa38561cd24c5eb228223585f26c5ec71 and fixed in 6.1.167 with commit c59090c50f62a17129fc4c5407bc4071305a9e82
	Issue introduced in 5.11 with commit d014538aa38561cd24c5eb228223585f26c5ec71 and fixed in 6.6.130 with commit 52db5ef163c96f916d424e472fb17aadc35a9f7a
	Issue introduced in 5.11 with commit d014538aa38561cd24c5eb228223585f26c5ec71 and fixed in 6.12.78 with commit b48a0f8d4541a4f6651dc9a64430ce9fdf5c120b
	Issue introduced in 5.11 with commit d014538aa38561cd24c5eb228223585f26c5ec71 and fixed in 6.18.19 with commit 73a7a345816946d276ad2c46c8bb771de67cfc46
	Issue introduced in 5.11 with commit d014538aa38561cd24c5eb228223585f26c5ec71 and fixed in 6.19.9 with commit 24a7b9daa103fa963b3fd37d8805b23e01621976
	Issue introduced in 5.11 with commit d014538aa38561cd24c5eb228223585f26c5ec71 and fixed in 7.0 with commit 25dd70a03b1f5f3aa71e1a5091ecd9cd2a13ee43

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-43380
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/hwmon/pmbus/q54sj108a2.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/a0fc1b9c738fba231f190ab960c83202722efee5
	https://git.kernel.org/stable/c/c59090c50f62a17129fc4c5407bc4071305a9e82
	https://git.kernel.org/stable/c/52db5ef163c96f916d424e472fb17aadc35a9f7a
	https://git.kernel.org/stable/c/b48a0f8d4541a4f6651dc9a64430ce9fdf5c120b
	https://git.kernel.org/stable/c/73a7a345816946d276ad2c46c8bb771de67cfc46
	https://git.kernel.org/stable/c/24a7b9daa103fa963b3fd37d8805b23e01621976
	https://git.kernel.org/stable/c/25dd70a03b1f5f3aa71e1a5091ecd9cd2a13ee43