Re: [PATCH 2/2] ext4: Fix zalloc()

[Richard Weinberger <richard@sigma-star.at>]

Tom,

Am Donnerstag, 11. Juli 2024, 17:45:17 CEST schrieb Tom Rini:
> The problem here is that "zalloc" is inline and so this change causes
> about 1KiB of growth on platforms which enable ext4 and so at least
> mx6sabresd now overflows it's maximum size. Looking harder, I think the
> best solution here would be for ext4 to stop using its own wrapper and
> instead call our kzalloc compatibility function.

As discussed on IRC yesterday, moving to kzalloc() is fine.
But the crash around malloc() still needs a fix.

Last night I investigated further why u-boot's malloc() implementation
crashes on my x86_64 test bed when ext4 tries to allocate a lot of memory.

It turned out that it's an integer overflow around malloc_extend_top()
and sbrk().
malloc_extend_top() uses a size_t to calculate the amount of required
memory and sbrk() takes an ptrdiff_t type.

On x86_64, u-boot seems to use unsigned long for size_t but just
an int for ptrdiff_t.
This is causing the trouble.

How about this?

diff --git a/arch/x86/include/asm/posix_types.h b/arch/x86/include/asm/posix_types.h
index dbcea7f47f..e1ed9bcabc 100644
--- a/arch/x86/include/asm/posix_types.h
+++ b/arch/x86/include/asm/posix_types.h
@@ -20,11 +20,12 @@ typedef unsigned short      __kernel_gid_t;
 #if defined(__x86_64__)
 typedef unsigned long  __kernel_size_t;
 typedef long           __kernel_ssize_t;
+typedef long           __kernel_ptrdiff_t;
 #else
 typedef unsigned int   __kernel_size_t;
 typedef int            __kernel_ssize_t;
-#endif
 typedef int            __kernel_ptrdiff_t;
+#endif
 typedef long           __kernel_time_t;
 typedef long           __kernel_suseconds_t;
 typedef long           __kernel_clock_t;

Thanks,
//richard

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