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/strncpy_from_user.c | 156 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 156 insertions(+) create mode 100644 lib/strncpy_from_user.c (limited to 'lib/strncpy_from_user.c') diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c new file mode 100644 index 000000000..5bb752ff7 --- /dev/null +++ b/lib/strncpy_from_user.c @@ -0,0 +1,156 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include + +#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS +#define IS_UNALIGNED(src, dst) 0 +#else +#define IS_UNALIGNED(src, dst) \ + (((long) dst | (long) src) & (sizeof(long) - 1)) +#endif + +/* + * Do a strncpy, return length of string without final '\0'. + * 'count' is the user-supplied count (return 'count' if we + * hit it), 'max' is the address space maximum (and we return + * -EFAULT if we hit it). + */ +static __always_inline long do_strncpy_from_user(char *dst, const char __user *src, + unsigned long count, unsigned long max) +{ + const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; + unsigned long res = 0; + + if (IS_UNALIGNED(src, dst)) + goto byte_at_a_time; + + while (max >= sizeof(unsigned long)) { + unsigned long c, data, mask; + + /* Fall back to byte-at-a-time if we get a page fault */ + unsafe_get_user(c, (unsigned long __user *)(src+res), byte_at_a_time); + + /* + * Note that we mask out the bytes following the NUL. This is + * important to do because string oblivious code may read past + * the NUL. For those routines, we don't want to give them + * potentially random bytes after the NUL in `src`. + * + * One example of such code is BPF map keys. BPF treats map keys + * as an opaque set of bytes. Without the post-NUL mask, any BPF + * maps keyed by strings returned from strncpy_from_user() may + * have multiple entries for semantically identical strings. + */ + if (has_zero(c, &data, &constants)) { + data = prep_zero_mask(c, data, &constants); + data = create_zero_mask(data); + mask = zero_bytemask(data); + *(unsigned long *)(dst+res) = c & mask; + return res + find_zero(data); + } + + *(unsigned long *)(dst+res) = c; + + res += sizeof(unsigned long); + max -= sizeof(unsigned long); + } + +byte_at_a_time: + while (max) { + char c; + + unsafe_get_user(c,src+res, efault); + dst[res] = c; + if (!c) + return res; + res++; + max--; + } + + /* + * Uhhuh. We hit 'max'. But was that the user-specified maximum + * too? If so, that's ok - we got as much as the user asked for. + */ + if (res >= count) + return res; + + /* + * Nope: we hit the address space limit, and we still had more + * characters the caller would have wanted. That's an EFAULT. + */ +efault: + return -EFAULT; +} + +/** + * strncpy_from_user: - Copy a NUL terminated string from userspace. + * @dst: Destination address, in kernel space. This buffer must be at + * least @count bytes long. + * @src: Source address, in user space. + * @count: Maximum number of bytes to copy, including the trailing NUL. + * + * Copies a NUL-terminated string from userspace to kernel space. + * + * On success, returns the length of the string (not including the trailing + * NUL). + * + * If access to userspace fails, returns -EFAULT (some data may have been + * copied). + * + * If @count is smaller than the length of the string, copies @count bytes + * and returns @count. + */ +long strncpy_from_user(char *dst, const char __user *src, long count) +{ + unsigned long max_addr, src_addr; + + might_fault(); + if (should_fail_usercopy()) + return -EFAULT; + if (unlikely(count <= 0)) + return 0; + + kasan_check_write(dst, count); + check_object_size(dst, count, false); + + if (can_do_masked_user_access()) { + long retval; + + src = masked_user_read_access_begin(src); + retval = do_strncpy_from_user(dst, src, count, count); + user_read_access_end(); + return retval; + } + + max_addr = TASK_SIZE_MAX; + src_addr = (unsigned long)untagged_addr(src); + 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(src, max)) { + retval = do_strncpy_from_user(dst, src, count, max); + user_read_access_end(); + return retval; + } + } + return -EFAULT; +} +EXPORT_SYMBOL(strncpy_from_user); -- cgit v1.3.1