check_mul_overflow(9)

💖 check_mul_overflow — like, the Kernel API Manual, section 9, bestie 💖

okay so bestie, welcome to check_mul_overflow(9) — yes it's a section 9 kernel API page, and yes it's lowkey iconic. pull up a chair, grab your iced coffee, and let's get into it 🫶

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✨ NAME ✨

check_mul_overflow — does your multiplication and also tells you if it overflowed. like a math bestie who does the work AND the vibe check 💅

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🌸 SYNOPSIS 🌸

check_mul_overflow (a , b , d );

that's it. three args. no notes. slay.

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🎀 ARGUMENTS 🎀

• a — the first factor, aka the first number you're multiplying. main character number #1 ✨
• b — the second factor, the other number. main character number #2 ✨
• d — a pointer where the product gets stored. it's giving "put the result here please" 🍓

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🦋 DESCRIPTION 🦋

okay so here's the tea, and it's actually a really good tea:

Returns true on wrap-around, and false otherwise. that's the whole vibe check — did the multiplication wrap around or not 🔥

and here's the part that matters: *d holds the results of the attempted multiplication, regardless of whether wrap-around occurred. like, it's gonna write the product either way. it doesn't withhold. it's not petty. it tells you the answer and whether it wrapped. no cap 💀

ngl this is the important bit — even if wrap-around happened, *d still got written. don't go assuming *d is untouched just because you got a true back 🙈

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🌈 SEE ALSO 🌈

real ones know the whole overflow family, and here's the entire crew — go say hi 👑

• Kernel file ./include/linux/overflow.h — that's where all this magic lives bestie 💜
• check_add_overflow(9)
• wrapping_add(9)
• wrapping_assign_add(9)
• check_sub_overflow(9)
• wrapping_sub(9)
• wrapping_assign_sub(9)
• wrapping_mul(9)
• check_shl_overflow(9)
• overflows_type(9)
• range_overflows(9)
• range_overflows_t(9)
• range_end_overflows(9)
• range_end_overflows_t(9)
• castable_to_type(9)
• size_mul(9)
• size_add(9)
• size_sub(9)
• array_size(9)
• array3_size(9)
• flex_array_size(9)
• struct_size(9)
• struct_size_t(9)
• struct_offset(9)
• __DEFINE_FLEX(9)
• _DEFINE_FLEX(9)
• DEFINE_RAW_FLEX(9)
• DEFINE_FLEX(9)
• STACK_FLEX_ARRAY_SIZE(9)
• typeof_flex_counter(9)
• overflows_flex_counter_type(9)
• __set_flex_counter(9)

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and that's the page, bestie! 🧚 this one ships out of ./include/linux and it's dated October 2026 — so yeah, mark your calendar, this manual page is literally from the future and it ate 💅💖