net: dns: Fix potential buffer overflow when unpacking labels #99683
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As the loop unpacking the DNS name from records checks the current label length on each iteration, it's also needed to update the remaining buffer length on each iteration, otherwise the buffer length checks doesn't work as expected. Additionally, the remaining buffer checks while technically worked, they were conceptually wrong and unintuitive. The buf->data pointer doesn't move, so comparing against this pointer when adding new labels doesn't make sense. It's more intuitive to simply compare the label size vs the remaining buffer space. Signed-off-by: Robert Lubos <[email protected]>
Verify that dns_unpack_name() generates a valid DNS name when unpacking records and that it returns an error in case of overflow. Signed-off-by: Robert Lubos <[email protected]>
rlubos
added
backport v3.7-branch
zephyrbot
added
area: Networking
area: Tests
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pdgendt
approved these changes
Nov 19, 2025
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As the loop unpacking the DNS name from records checks the current
label length on each iteration, it's also needed to update the remaining
buffer length on each iteration, otherwise the buffer length checks
doesn't work as expected.
Additionally, the remaining buffer checks while technically worked, they
were conceptually wrong and unintuitive. The buf->data pointer doesn't
move, so comparing against this pointer when adding new labels doesn't
make sense. It's more intuitive to simply compare the label size vs
the remaining buffer space.
Fixes #99682