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futex: Validate futex value against futex size

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Ensure the futex value fits in the given futex size. Since this adds a
constraint to an existing syscall, it might possibly change behaviour.

Currently the value would be truncated to a u32 and any high bits
would get silently lost.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230921105247.828934099@noisy.programming.kicks-ass.net
This commit is contained in:
peterz@infradead.org 2023-09-21 12:45:09 +02:00 committed by Peter Zijlstra
parent 5694289ce1
commit 698eb82638
2 changed files with 13 additions and 0 deletions
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10
kernel/futex/futex.h
View File

@ -85,6 +85,16 @@ static inline bool futex_flags_valid(unsigned int flags)
return true;
}
static inline bool futex_validate_input(unsigned int flags, u64 val)
{
int bits = 8 * futex_size(flags);
if (bits < 64 && (val >> bits))
return false;
return true;
}
#ifdef CONFIG_FAIL_FUTEX
extern bool should_fail_futex(bool fshared);
#else

3
kernel/futex/syscalls.c
View File

@ -209,6 +209,9 @@ static int futex_parse_waitv(struct futex_vector *futexv,
if (!futex_flags_valid(flags))
return -EINVAL;
if (!futex_validate_input(flags, aux.val))
return -EINVAL;
futexv[i].w.flags = flags;
futexv[i].w.val = aux.val;
futexv[i].w.uaddr = aux.uaddr;