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/strnlen_user.c | 129 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 129 insertions(+) create mode 100644 lib/strnlen_user.c (limited to 'lib/strnlen_user.c') diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c new file mode 100644 index 000000000..4a6574b67 --- /dev/null +++ b/lib/strnlen_user.c @@ -0,0 +1,129 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include + +#include + +/* + * Do a strnlen, return length of string *with* final '\0'. + * 'count' is the user-supplied count, while 'max' is the + * address space maximum. + * + * Return 0 for exceptions (which includes hitting the address + * space maximum), or 'count+1' if hitting the user-supplied + * maximum count. + * + * NOTE! We can sometimes overshoot the user-supplied maximum + * if it fits in a aligned 'long'. The caller needs to check + * the return value against "> max". + */ +static __always_inline long do_strnlen_user(const char __user *src, unsigned long count, unsigned long max) +{ + const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; + unsigned long align, res = 0; + unsigned long c; + + /* + * Do everything aligned. But that means that we + * need to also expand the maximum.. + */ + align = (sizeof(unsigned long) - 1) & (unsigned long)src; + src -= align; + max += align; + + unsafe_get_user(c, (unsigned long __user *)src, efault); + c |= aligned_byte_mask(align); + + for (;;) { + unsigned long data; + if (has_zero(c, &data, &constants)) { + data = prep_zero_mask(c, data, &constants); + data = create_zero_mask(data); + return res + find_zero(data) + 1 - align; + } + res += sizeof(unsigned long); + /* We already handled 'unsigned long' bytes. Did we do it all ? */ + if (unlikely(max <= sizeof(unsigned long))) + break; + max -= sizeof(unsigned long); + unsafe_get_user(c, (unsigned long __user *)(src+res), efault); + } + res -= align; + + /* + * Uhhuh. We hit 'max'. But was that the user-specified maximum + * too? If so, return the marker for "too long". + */ + if (res >= count) + return count+1; + + /* + * Nope: we hit the address space limit, and we still had more + * characters the caller would have wanted. That's 0. + */ +efault: + return 0; +} + +/** + * strnlen_user: - Get the size of a user string INCLUDING final NUL. + * @str: The string to measure. + * @count: Maximum count (including NUL character) + * + * Context: User context only. This function may sleep if pagefaults are + * enabled. + * + * Get the size of a NUL-terminated string in user space. + * + * Returns the size of the string INCLUDING the terminating NUL. + * If the string is too long, returns a number larger than @count. User + * has to check the return value against "> count". + * On exception (or invalid count), returns 0. + * + * NOTE! You should basically never use this function. There is + * almost never any valid case for using the length of a user space + * string, since the string can be changed at any time by other + * threads. Use "strncpy_from_user()" instead to get a stable copy + * of the string. + */ +long strnlen_user(const char __user *str, long count) +{ + unsigned long max_addr, src_addr; + + if (unlikely(count <= 0)) + return 0; + + if (can_do_masked_user_access()) { + long retval; + + str = masked_user_read_access_begin(str); + retval = do_strnlen_user(str, count, count); + user_read_access_end(); + return retval; + } + + max_addr = TASK_SIZE_MAX; + src_addr = (unsigned long)untagged_addr(str); + if (likely(src_addr < max_addr)) { + unsigned long max = max_addr - src_addr; + long retval; + + /* + * Truncate 'max' to the user-specified limit, so that + * we only have one limit we need to check in the loop + */ + if (max > count) + max = count; + + if (user_read_access_begin(str, max)) { + retval = do_strnlen_user(str, count, max); + user_read_access_end(); + return retval; + } + } + return 0; +} +EXPORT_SYMBOL(strnlen_user); -- cgit v1.3.1