strndup_user(9)

💖 strndup_user(9) 💖

okay so bestie, welcome to the strndup_user page from the Kernel API Manual — yes, that's <italic>9</italic>, the kernel developer section, we're in the big leagues now 🫶

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✨ NAME ✨

strndup_user — duplicate an existing string from user space 💅

like yeah, it copies a string for you, but the string lives in user space and you're over here in kernel land, so it's a whole thing, iykyk 🦋

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🌸 SYNOPSIS 🌸

char * strndup_user (const char __user *s , long n );

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🎀 ARGUMENTS 🎀

• s — the string you wanna duplicate, babes. that's the one. the source. the moment. ✨
• n — maximum number of bytes to copy, and yes this includes the trailing NUL — do not forget the NUL, the NUL is part of the count, no cap 🙈

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💜 RETURN 💜

a newly allocated copy of s 💖 — or, plot twist, an ERR_PTR in case of error 😭 so like, always check that bad boy before you dereference it, fr fr.

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🌈 SEE ALSO 🌈

okay this list is long long, so buckle up bestie, we're going on a journey through the kernel:

• Kernel file ./mm/util.c
• kfree_const(9)
• __kmemdup_nul(9)
• kstrdup(9)
• kstrdup_const(9)
• kstrndup(9)
• kmemdup(9)
• kmemdup_array(9)
• kvmemdup(9)
• kmemdup_nul(9)
• memdup_user(9)
• vmemdup_user(9)
• memdup_user_nul(9)
• randomize_page(9)
• __account_locked_vm(9)
• account_locked_vm(9)
• __vmalloc_array(9)
• vmalloc_array(9)
• __vcalloc(9)
• vcalloc(9)
• folio_mapping(9)
• folio_copy(9)
• get_cmdline(9)
• mem_dump_obj(9)
• compat_set_desc_from_vma(9)
• __compat_vma_mmap(9)
• compat_vma_mmap(9)
• snapshot_page(9)
• mmap_action_prepare(9)
• mmap_action_complete(9)
• folio_pte_batch(9)
• page_range_contiguous(9)

like I said. long long. but every single one is iconic in its own way 👑

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bestie reminder: n counts the trailing NUL, and a failed call gives you an ERR_PTR, not a NULL. check it properly or the kernel will simply not be slaying anymore 💀

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that's the whole page, bestie, go forth and duplicate responsibly 🧚 from the ./mm corner of the source tree, dated October 2026, signing off as your girl strndup_user(9) — mwah 💋🍓