CVE-2024-35849

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix information leak in btrfs_ioctl_logical_to_ino()

Syzbot reported the following information leak for in btrfs_ioctl_logical_to_ino():

BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline] BUG: KMSAN: kernel-infoleak in _copy_to_user+0xbc/0x110 lib/usercopy.c:40 instrument_copy_to_user include/linux/instrumented.h:114 [inline] _copy_to_user+0xbc/0x110 lib/usercopy.c:40 copy_to_user include/linux/uaccess.h:191 [inline] btrfs_ioctl_logical_to_ino+0x440/0x750 fs/btrfs/ioctl.c:3499 btrfs_ioctl+0x714/0x1260 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:904 [inline] __se_sys_ioctl+0x261/0x450 fs/ioctl.c:890 __x64_sys_ioctl+0x96/0xe0 fs/ioctl.c:890 x64_sys_call+0x1883/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:17 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at: __kmalloc_large_node+0x231/0x370 mm/slub.c:3921 __do_kmalloc_node mm/slub.c:3954 [inline] __kmalloc_node+0xb07/0x1060 mm/slub.c:3973 kmalloc_node include/linux/slab.h:648 [inline] kvmalloc_node+0xc0/0x2d0 mm/util.c:634 kvmalloc include/linux/slab.h:766 [inline] init_data_container+0x49/0x1e0 fs/btrfs/backref.c:2779 btrfs_ioctl_logical_to_ino+0x17c/0x750 fs/btrfs/ioctl.c:3480 btrfs_ioctl+0x714/0x1260 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:904 [inline] __se_sys_ioctl+0x261/0x450 fs/ioctl.c:890 __x64_sys_ioctl+0x96/0xe0 fs/ioctl.c:890 x64_sys_call+0x1883/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:17 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Bytes 40-65535 of 65536 are uninitialized Memory access of size 65536 starts at ffff888045a40000

This happens, because were copying a struct btrfs_data_container back to user-space. This btrfs_data_container is allocated in init_data_container() via kvmalloc(), which does not zero-fill the memory.

Fix this by using kvzalloc() which zeroes out the memory on allocation.

Affected Software

References

• https://git.kernel.org/stable/c/2f7ef5bb4a2f3e481ef05fab946edb97c84f67cf
• https://git.kernel.org/stable/c/30189e54ba80e3209d34cfeea87b848f6ae025e6
• https://git.kernel.org/stable/c/3a63cee1a5e14a3e52c19142c61dd5fcb524f6dc
• https://git.kernel.org/stable/c/689efe22e9b5b7d9d523119a9a5c3c17107a0772
• https://git.kernel.org/stable/c/73db209dcd4ae026021234d40cfcb2fb5b564b86
• https://git.kernel.org/stable/c/8bdbcfaf3eac42f98e5486b3d7e130fa287811f6
• https://git.kernel.org/stable/c/e58047553a4e859dafc8d1d901e1de77c9dd922d
• https://git.kernel.org/stable/c/fddc19631c51d9c17d43e9f822a7bc403af88d54
• https://git.kernel.org/stable/c/2f7ef5bb4a2f3e481ef05fab946edb97c84f67cf
• https://git.kernel.org/stable/c/30189e54ba80e3209d34cfeea87b848f6ae025e6
• https://git.kernel.org/stable/c/3a63cee1a5e14a3e52c19142c61dd5fcb524f6dc
• https://git.kernel.org/stable/c/689efe22e9b5b7d9d523119a9a5c3c17107a0772
• https://git.kernel.org/stable/c/73db209dcd4ae026021234d40cfcb2fb5b564b86
• https://git.kernel.org/stable/c/8bdbcfaf3eac42f98e5486b3d7e130fa287811f6
• https://git.kernel.org/stable/c/e58047553a4e859dafc8d1d901e1de77c9dd922d
• https://git.kernel.org/stable/c/fddc19631c51d9c17d43e9f822a7bc403af88d54
• https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html
• https://lists.debian.org/debian-lts-announce/2024/06/msg00020.html