Switch System Flaws: Difference between revisions

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| Null-dereference in panic()

| The Switch's stage 1 bootloader, on panic(), clears the stack and then attempts to clear the Security Engine. However, it does so by dereferencing a pointer to the SE in .bss (initially NULL), and this pointer doesn't get initialized until partway into the bootloader's main(). Thus, a panic() caused prior to SE initialization would result in the SE pointer still being NULL when dereferenced. This would cause a data abort, causing the bootloader to clear the stack and then try to clear the security engine...dereferencing NULL again, over and over in a loop.

| The Switch's stage 1 bootloader, on panic(), clears the stack and then attempts to clear the Security Engine. However, it does so by dereferencing a pointer to the SE in .bss (initially NULL), and this pointer doesn't get initialized until partway into the bootloader's main() after several functions that might panic() are called. Thus, a panic() caused prior to SE initialization would result in the SE pointer still being NULL when dereferenced. This would cause a data abort, causing the bootloader to clear the stack and then try to clear the security engine...dereferencing NULL again, over and over in a loop.

In 3.0.0, this was fixed by moving the security engine initialization earlier in main(), before the first function that could potentially panic().

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 |-
 |  Null-dereference in panic()
-|  The Switch's stage 1 bootloader, on panic(), clears the stack and then attempts to clear the Security Engine. However, it does so by dereferencing a pointer to the SE in .bss (initially NULL), and this pointer doesn't get initialized until partway into the bootloader's main(). Thus, a panic() caused prior to SE initialization would result in the SE pointer still being NULL when dereferenced. This would cause a data abort, causing the bootloader to clear the stack and then try to clear the security engine...dereferencing NULL again, over and over in a loop.
+|  The Switch's stage 1 bootloader, on panic(), clears the stack and then attempts to clear the Security Engine. However, it does so by dereferencing a pointer to the SE in .bss (initially NULL), and this pointer doesn't get initialized until partway into the bootloader's main() after several functions that might panic() are called. Thus, a panic() caused prior to SE initialization would result in the SE pointer still being NULL when dereferenced. This would cause a data abort, causing the bootloader to clear the stack and then try to clear the security engine...dereferencing NULL again, over and over in a loop.
 In 3.0.0, this was fixed by moving the security engine initialization earlier in main(), before the first function that could potentially panic().