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Subject[PATCH] initramfs: CPIO unpacking fix
Date

Unlink files, symlinks, FIFOs, devices etc. (except directories) before
writing them when extracting CPIOs. This stops weird behaviour like:
1) writing through symlinks created in earlier CPIOs. eg foo->bar in
the first CPIO. Having foo as a non-link in a subsequent CPIO,
results in bar being written and foo remaining as a symlink.
2) if the first version of file foo is larger than foo in a
subsequent CPIO, we end up with a mix of the two. ie. neither
the first or second version of /foo.
3) special files like devices, fifo etc. can't be overwritten in
subsequent CPIOS.

With this, the kernel will more closely replicate
for i in *.cpio; do cpio --extract --unconditional < $i ; done

This is a change but it's regarded as fixing broken functionality.

Signed-off-by: Michael Neuling <mikey@neuling.org>
---
This is a retransmission.

init/initramfs.c | 3 +++
1 files changed, 3 insertions(+)

Index: linux-2.6.15/init/initramfs.c
===================================================================
--- linux-2.6.15.orig/init/initramfs.c
+++ linux-2.6.15/init/initramfs.c
@@ -249,6 +249,7 @@ static int __init do_name(void)
if (dry_run)
return 0;
if (S_ISREG(mode)) {
+ sys_unlink(collected);
if (maybe_link() >= 0) {
wfd = sys_open(collected, O_WRONLY|O_CREAT, mode);
if (wfd >= 0) {
@@ -263,6 +264,7 @@ static int __init do_name(void)
sys_chmod(collected, mode);
} else if (S_ISBLK(mode) || S_ISCHR(mode) ||
S_ISFIFO(mode) || S_ISSOCK(mode)) {
+ sys_unlink(collected);
if (maybe_link() == 0) {
sys_mknod(collected, mode, rdev);
sys_chown(collected, uid, gid);
@@ -291,6 +293,7 @@ static int __init do_copy(void)
static int __init do_symlink(void)
{
collected[N_ALIGN(name_len) + body_len] = '\0';
+ sys_unlink(collected);
sys_symlink(collected + N_ALIGN(name_len), collected);
sys_lchown(collected, uid, gid);
state = SkipIt;

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