kernel/linux.git/init/initramfs.c, branch v5.10.257

initramfs: avoid filename buffer overrun

2024-12-14T18:47:43+00:00

[ Upstream commit e017671f534dd3f568db9e47b0583e853d2da9b5 ] The initramfs filename field is defined in Documentation/driver-api/early-userspace/buffer-format.rst as: 37 cpio_file := ALGN(4) + cpio_header + filename + "\0" + ALGN(4) + data ... 55 ============= ================== ========================= 56 Field name Field size Meaning 57 ============= ================== ========================= ... 70 c_namesize 8 bytes Length of filename, including final \0 When extracting an initramfs cpio archive, the kernel's do_name() path handler assumes a zero-terminated path at @collected, passing it directly to filp_open() / init_mkdir() / init_mknod(). If a specially crafted cpio entry carries a non-zero-terminated filename and is followed by uninitialized memory, then a file may be created with trailing characters that represent the uninitialized memory. The ability to create an initramfs entry would imply already having full control of the system, so the buffer overrun shouldn't be considered a security vulnerability. Append the output of the following bash script to an existing initramfs and observe any created /initramfs_test_fname_overrunAA* path. E.g. ./reproducer.sh | gzip >> /myinitramfs It's easiest to observe non-zero uninitialized memory when the output is gzipped, as it'll overflow the heap allocated @out_buf in __gunzip(), rather than the initrd_start+initrd_size block. ---- reproducer.sh ---- nilchar="A" # change to "\0" to properly zero terminate / pad magic="070701" ino=1 mode=$(( 0100777 )) uid=0 gid=0 nlink=1 mtime=1 filesize=0 devmajor=0 devminor=1 rdevmajor=0 rdevminor=0 csum=0 fname="initramfs_test_fname_overrun" namelen=$(( ${#fname} + 1 )) # plus one to account for terminator printf "%s%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%s" \ $magic $ino $mode $uid $gid $nlink $mtime $filesize \ $devmajor $devminor $rdevmajor $rdevminor $namelen $csum $fname termpadlen=$(( 1 + ((4 - ((110 + $namelen) & 3)) % 4) )) printf "%.s${nilchar}" $(seq 1 $termpadlen) ---- reproducer.sh ---- Symlink filename fields handled in do_symlink() won't overrun past the data segment, due to the explicit zero-termination of the symlink target. Fix filename buffer overrun by aborting the initramfs FSM if any cpio entry doesn't carry a zero-terminator at the expected (name_len - 1) offset. Fixes: 1da177e4c3f41 ("Linux-2.6.12-rc2") Signed-off-by: David Disseldorp Link: https://lore.kernel.org/r/20241030035509.20194-2-ddiss@suse.de Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin

init: open /initrd.image with O_LARGEFILE

2024-04-13T10:59:02+00:00

commit 4624b346cf67400ef46a31771011fb798dd2f999 upstream. If initrd data is larger than 2Gb, we'll eventually fail to write to the /initrd.image file when we hit that limit, unless O_LARGEFILE is set. Link: https://lkml.kernel.org/r/20240317221522.896040-1-jsperbeck@google.com Signed-off-by: John Sperbeck Cc: Jens Axboe Cc: Nick Desaulniers Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

initramfs: fix clang build failure

2020-12-11T22:02:14+00:00

There is only one function in init/initramfs.c that is in the .text section, and it is marked __weak. When building with clang-12 and the integrated assembler, this leads to a bug with recordmcount: ./scripts/recordmcount "init/initramfs.o" Cannot find symbol for section 2: .text. init/initramfs.o: failed I'm not quite sure what exactly goes wrong, but I notice that this function is only ever called from an __init function, and normally inlined. Marking it __init as well is clearly correct and it leads to recordmcount no longer complaining. Link: https://lkml.kernel.org/r/20201204165742.3815221-1-arnd@kernel.org Signed-off-by: Arnd Bergmann Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Barret Rhoden Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

init: fix error check in clean_path()

2020-09-04T16:16:58+00:00

init_stat() returns 0 on success, same as vfs_lstat(). When it replaced vfs_lstat(), the '!' was dropped. Fixes: 716308a5331b ("init: add an init_stat helper") Signed-off-by: Barret Rhoden Reviewed-by: Christoph Hellwig Signed-off-by: Linus Torvalds

init: add an init_utimes helper

2020-07-31T06:17:54+00:00

Add a simple helper to set timestamps with a kernel space file name and switch the early init code over to it. Signed-off-by: Christoph Hellwig

init: add an init_stat helper

2020-07-31T06:17:54+00:00

Add a simple helper to stat with a kernel space file name and switch the early init code over to it. Signed-off-by: Christoph Hellwig

init: add an init_mknod helper

2020-07-31T06:17:54+00:00

Add a simple helper to mknod with a kernel space file name and switch the early init code over to it. Remove the now unused ksys_mknod. Signed-off-by: Christoph Hellwig

init: add an init_mkdir helper

2020-07-31T06:17:53+00:00

Add a simple helper to mkdir with a kernel space file name and switch the early init code over to it. Remove the now unused ksys_mkdir. Signed-off-by: Christoph Hellwig

init: add an init_symlink helper

2020-07-31T06:17:53+00:00

Add a simple helper to symlink with a kernel space file name and switch the early init code over to it. Remove the now unused ksys_symlink. Signed-off-by: Christoph Hellwig

init: add an init_link helper

2020-07-31T06:17:53+00:00

Add a simple helper to link with a kernel space file name and switch the early init code over to it. Remove the now unused ksys_link. Signed-off-by: Christoph Hellwig