My hunch about the length of struct aliases was correct; when a
parameter that is longer than the *entire* aliases struct element (146
characters) is compared the call to memcmp() is redirected to
"include/linux/fortify-string.h" [0] where checks are done to ensure
there are no out-of-bounds reads.
Because the 'buf' parameter is 146 characters long the call looks like:
memcmp("param146=...", aliases[i].alias, len + 1)
where 'len' is 146 and so 147 gets passed in. That triggers:
if (p_size < size || q_size < size)
fortify_panic(__func__);
because 'size' (from 'len + 1') is 147 and q_size is 146 ( size_t q_size
= __struct_size(q) )
('p' is `buf`, 'q' is 'aliases[i].alias' )
So, with a guard case to avoid calling memcmp() at all unless the
lengths match it works. I'll send the patch to the v6.8 stable tree
upstream.
$ qemu-system-aarch64 -machine virt,gic-version=3 -cpu max,pauth-impdef=on -smp
2 -m 4096 -nographic -kernel
/srv/NAS/Sunny/SourceCode/builds/linux-aarch64/arch/arm64/boot/Image -append
"debug
param146=ni4ohneo0oothieyeef9vo4ieth4yeiz6ohsiemae6aoy2asu9xei5eethoh0igaitha7laeghoot
haeph9xai7kier3aib7aejaengahghan2zojeebai3kad9meesh6eichaey2"
[ 0.000000] Booting Linux on physical CPU 0x0000000000 [0x000f0510]
[ 0.000000] Linux version 6.8.12 ([email protected]) (aarch64-linux-gnu-gcc
(Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40) #10 SMP Fri
Jul 26 13:57:53 BST 2024
[ 0.000000] random: crng init done
[ 0.000000] Machine model: linux,dummy-virt
...
[ 0.000000] Kernel command line: debug
param146=ni4ohneo0oothieyeef9vo4ieth4yeiz6ohsiemae6aoy2asu9xei5eethoh0igaitha7laeghoothaeph9xai7kier3aib7aejae
ngahghan2zojeebai3kad9meesh6eichaey2
[ 0.000000] Unknown kernel command line parameters
"param146=ni4ohneo0oothieyeef9vo4ieth4yeiz6ohsiemae6aoy2asu9xei5eethoh0igaitha7laeghoothaeph9xai7k
ier3aib7aejaengahghan2zojeebai3kad9meesh6eichaey2", will be passed to user
space.
[0]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/fortify-string.h?h=v6.8#n659
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https://bugs.launchpad.net/bugs/2069534
Title:
linux 6.8 fails to boot on arm64 if any param is more than 140 chars
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