Description
In the Linux kernel, the following vulnerability has been resolved: serial: core: fix infinite loop in handle_tx() for PORT_UNKNOWN uart_write_room() and uart_write() behave inconsistently when xmit_buf is NULL (which happens for PORT_UNKNOWN ports that were never properly initialized): - uart_write_room() returns kfifo_avail() which can be > 0 - uart_write() checks xmit_buf and returns 0 if NULL This inconsistency causes an infinite loop in drivers that rely on tty_write_room() to determine if they can write: while (tty_write_room(tty) > 0) { written = tty->ops->write(...); // written is always 0, loop never exits } For example, caif_serial's handle_tx() enters an infinite loop when used with PORT_UNKNOWN serial ports, causing system hangs. Fix by making uart_write_room() also check xmit_buf and return 0 if it's NULL, consistent with uart_write(). Reproducer: https://gist.github.com/mrpre/d9a694cc0e19828ee3bc3b37983fde13
Product status
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (git) before efe85a557186b7fe915572ae93a8f3f78bfd9a22
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (git) before bc70f2b36cf474d5cc8ecbcaf57f3e326fdec67c
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (git) before 455ce986fa356ff43a43c0d363ba95fa152f21d5
2.6.12
Any version before 2.6.12
6.18.20 (semver)
6.19.10 (semver)
7.0 (original_commit_for_fix)
References
git.kernel.org/...c/efe85a557186b7fe915572ae93a8f3f78bfd9a22
git.kernel.org/...c/bc70f2b36cf474d5cc8ecbcaf57f3e326fdec67c
git.kernel.org/...c/455ce986fa356ff43a43c0d363ba95fa152f21d5