I have some UNIX machines which I remotely boot via tftp boot, for which I enable the tftp feature of dnsmasq. Interestingly dnsmasq fails to deliver (the same file for all machines)) to some machines but for others not. I traced the bug down, and basically it fails with error "unsupported request from IP.x.y.z" (line 366 in tftp.c). Here is an example package which is sent (516 hex bytes): 76 6d 6c 69 6e 75 78 00 6f 63 74 65 74 00 12 74 10 3c 00 00 00 00 00 01 a9 24 00 00 00 00 00 00 1e 38 00 00 00 00 00 00 1c a0 00 00 00 00 00 00 1d 08 00 00 00 00 00 00 1d 28 00 00 00 00 00 00 08 00 00 00 00 00 00 00 03 d8 00 00 00 00 00 00 00 00 00 00 00 00 00 00 1d 30 00 00 00 02 ff e0 00 00 00 00 03 60 a8 49 55 93 00 00 00 01 f0 d4 21 e4 00 00 00 00 00 00 1d 78 00 00 00 f0 f0 d8 51 38 00 00 00 f0 f0 d4 21 c0 00 00 00 00 00 00 00 00 00 00 00 00 00 01 aa b8 00 00 00 f0 f0 e9 62 7c 00 00 00 00 00 00 03 01 ff ff ff ff ff ff 03 00 ff ff ff ff ff ff ff ff 00 00 00 00 00 00 00 03 00 00 00 00 00 00 00 05 00 00 00 00 00 00 00 04 ff ff ff ff ff ff ff ff 00 00 00 00 00 00 00 00 ff ff ff ff ff ff ff ff 00 00 00 00 00 00 00 05 00 00 00 00 00 00 1e 38 00 00 00 00 00 00 00 60 00 00 00 00 00 01 a6 68 00 00 00 00 00 00 00 03 00 00 00 00 00 00 00 ff 00 00 00 00 00 00 00 03 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 02 00 00 00 00 00 00 00 00 00 00 00 f0 f0 d8 4f 30 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 01 ae ec 00 00 00 00 00 00 1f 70 00 00 00 00 00 00 1e b8 00 00 03 60 a8 49 55 93 00 00 00 02 18 71 1a 00 00 00 00 00 00 00 00 03 00 00 00 00 00 00 00 03 00 00 00 00 00 00 1e 38 00 00 00 00 00 00 00 07 00 00 00 00 00 00 00 00 00 00 00 f0 f0 d2 f0 70 00 00 00 00 00 00 1f c0 00 00 00 f0 f0 d4 0b e8 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 60 ff ff ff fc 00 60 18 00 00 00 00 00 00 00 00 00 00 00 00 f0 f0 d8 8f d0 00 00 00 00 00 00 1f f8 00 00 00 00 00 00 00 00 00 00 00 f0 f0 d8 8d b8 00 00 00 00 00 00 1e e8 00 00 Please note the last 3 bytes: "e8 00 00". If the 3rd-last byte is "00", then dnsmasq works. For the failing machines the send "e8", So, the bug is in line 366 of tftp.c: filename = next(&p, end) Here filename gets the value NULL from next(), because the "end" variable is off-by-2. The fix is to change line 363 to become: end = packet + 2 + len; Patch with fix and hint where it fails is attached. Please apply (the first hunk of the patch) for the next upload. Thanks, Helge Reproducible: Always Steps to Reproduce: run dnsmasq
Created attachment 2037999 [details] Patch to fix tftp off-by-2 bug
This message is a reminder that Fedora Linux 39 is nearing its end of life. Fedora will stop maintaining and issuing updates for Fedora Linux 39 on 2024-11-26. It is Fedora's policy to close all bug reports from releases that are no longer maintained. At that time this bug will be closed as EOL if it remains open with a 'version' of '39'. Package Maintainer: If you wish for this bug to remain open because you plan to fix it in a currently maintained version, change the 'version' to a later Fedora Linux version. Note that the version field may be hidden. Click the "Show advanced fields" button if you do not see it. Thank you for reporting this issue and we are sorry that we were not able to fix it before Fedora Linux 39 is end of life. If you would still like to see this bug fixed and are able to reproduce it against a later version of Fedora Linux, you are encouraged to change the 'version' to a later version prior to this bug being closed.
Fedora Linux 39 entered end-of-life (EOL) status on 2024-11-26. Fedora Linux 39 is no longer maintained, which means that it will not receive any further security or bug fix updates. As a result we are closing this bug. If you can reproduce this bug against a currently maintained version of Fedora Linux please feel free to reopen this bug against that version. Note that the version field may be hidden. Click the "Show advanced fields" button if you do not see the version field. If you are unable to reopen this bug, please file a new report against an active release. Thank you for reporting this bug and we are sorry it could not be fixed.