[PATCH mtd-utils] misc-utils: Fix integer overflow in docfdisk.c

[Anton Moryakov]

Report of the static analyzer:
Possible integer underflow: left operand is tainted. An integer underflow may occur due to arithmetic operation (subtraction) between variable 'block' and value '1', when 'block' is tainted { [-2147483648, 2147483647] }

Corrections explained:
Added the block <= 0 check, which prevents integer underflow when calculating block - 1 and ensures that block is always positive.

Triggers found by static analyzer Svace.

Signed-off-by: Anton Moryakov <ant.v.moryakov at gmail.com>

---
 misc-utils/docfdisk.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/misc-utils/docfdisk.c b/misc-utils/docfdisk.c
index 486ce29..e473ceb 100644
--- a/misc-utils/docfdisk.c
+++ b/misc-utils/docfdisk.c
@@ -255,6 +255,10 @@ int main(int argc, char **argv)
 		ip->firstUnit = cpu_to_le32(block);
 		if (!nblocks[i])
 			nblocks[i] = totblocks - block;
+		if (block <= 0) {
+			fprintf(stderr, "Error: Invalid block value (%d). Block must be greater than 0.\n", block);
+			return -1;
+		}
 		ip->virtualUnits = cpu_to_le32(nblocks[i]);
 		block += nblocks[i];
 		ip->lastUnit = cpu_to_le32(block-1);
-- 
2.30.2