From 27600805e62f800bacf990354632eae4e487d34c Mon Sep 17 00:00:00 2001 From: Yazen Ghannam Date: Thu, 3 Sep 2026 10:43:25 -0500 Subject: x86/amd_node: Fix PCI device reference counting in amd_smn_init() The local "root" pointer is a temporary variable used during the device search. Therefore, refcount related to the search iterators should be cleaned up after the search is complete. Use the __free() cleanup macro to ensure the refcount is decremented when the temporary pointer goes out of scope. Additionally, increment the refcount when caching a root pointer. This ensures the in-use refcount is separate from the temporary search refcounting. Finally, drop the redundant "root = NULL" before the second search loop. The pci_get_class() iterator always decrements the refcount of its "from" argument, so the first loop can only fall through with "root" already NULL. Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching") Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com Reported-by: Sashiko Assisted-by: LLM Signed-off-by: Yazen Ghannam Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Mario Limonciello (AMD) Cc: Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com --- lib/crc/crc4.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 lib/crc/crc4.c (limited to 'lib/crc/crc4.c') diff --git a/lib/crc/crc4.c b/lib/crc/crc4.c new file mode 100644 index 000000000..8e83fbe60 --- /dev/null +++ b/lib/crc/crc4.c @@ -0,0 +1,45 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * crc4.c - simple crc-4 calculations. + */ + +#include +#include +#include + +static const uint8_t crc4_tab[] = { + 0x0, 0x7, 0xe, 0x9, 0xb, 0xc, 0x5, 0x2, + 0x1, 0x6, 0xf, 0x8, 0xa, 0xd, 0x4, 0x3, +}; + +/** + * crc4 - calculate the 4-bit crc of a value. + * @c: starting crc4 + * @x: value to checksum + * @bits: number of bits in @x to checksum + * + * Returns the crc4 value of @x, using polynomial 0b10111. + * + * The @x value is treated as left-aligned, and bits above @bits are ignored + * in the crc calculations. + */ +uint8_t crc4(uint8_t c, uint64_t x, int bits) +{ + int i; + + /* mask off anything above the top bit */ + x &= (1ull << bits) - 1; + + /* Align to 4-bits */ + bits = (bits + 3) & ~0x3; + + /* Calculate crc4 over four-bit nibbles, starting at the MSbit */ + for (i = bits - 4; i >= 0; i -= 4) + c = crc4_tab[c ^ ((x >> i) & 0xf)]; + + return c; +} +EXPORT_SYMBOL_GPL(crc4); + +MODULE_DESCRIPTION("CRC4 calculations"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1