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fix(core/bootloader): explicit casts on version compare to control signed/unsigned arithmetic mix

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Ondrej Mikle 2023-10-27 15:02:20 +02:00 committed by matejcik
parent 02f34a2748
commit 6658ad84d1
1 changed files with 13 additions and 8 deletions
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21
core/embed/bootloader/messages.c
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@ -432,18 +432,23 @@ static bool _read_payload(pb_istream_t *stream, const pb_field_t *field,
} }
static int version_compare(uint32_t vera, uint32_t verb) { static int version_compare(uint32_t vera, uint32_t verb) {
/* Explicit casts so that we control how compiler does the unsigned shift
* and correctly then promote uint8_t to int without possibility of
* having implementation-defined right shift on negative int
* in case compiler promoted the wrong unsinged int
*/
int a, b; int a, b;
a = vera & 0xFF; a = (uint8_t)vera & 0xFF;
b = verb & 0xFF; b = (uint8_t)verb & 0xFF;
if (a != b) return a - b; if (a != b) return a - b;
a = (vera >> 8) & 0xFF; a = (uint8_t)(vera >> 8) & 0xFF;
b = (verb >> 8) & 0xFF; b = (uint8_t)(verb >> 8) & 0xFF;
if (a != b) return a - b; if (a != b) return a - b;
a = (vera >> 16) & 0xFF; a = (uint8_t)(vera >> 16) & 0xFF;
b = (verb >> 16) & 0xFF; b = (uint8_t)(verb >> 16) & 0xFF;
if (a != b) return a - b; if (a != b) return a - b;
a = (vera >> 24) & 0xFF; a = (uint8_t)(vera >> 24) & 0xFF;
b = (verb >> 24) & 0xFF; b = (uint8_t)(verb >> 24) & 0xFF;
return a - b; return a - b;
} }