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Merge pull request #9213 from poettering/copy-mount

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copy() mount detection fixes
This commit is contained in:
Lennart Poettering 2018-06-08 12:09:23 +02:00 committed by GitHub
parent d23c3e4c28 575a07d2dc
commit 0323073878
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 50 additions and 12 deletions
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55
src/basic/copy.c
View file

@ -29,6 +29,7 @@
#include "io-util.h"
#include "macro.h"
#include "missing.h"
#include "mount-util.h"
#include "string-util.h"
#include "strv.h"
#include "time-util.h"
@ -36,7 +37,12 @@
#include "user-util.h"
#include "xattr-util.h"
#define COPY_BUFFER_SIZE (16*1024u)
#define COPY_BUFFER_SIZE (16U*1024U)
/* A safety net for descending recursively into file system trees to copy. On Linux PATH_MAX is 4096, which means the
* deepest valid path one can build is around 2048, which we hence use as a safety net here, to not spin endlessly in
* case of bind mount cycles and suchlike. */
#define COPY_DEPTH_MAX 2048U
static ssize_t try_copy_file_range(
int fd_in, loff_t *off_in,
@ -479,6 +485,7 @@ static int fd_copy_directory(
int dt,
const char *to,
dev_t original_device,
unsigned depth_left,
uid_t override_uid,
gid_t override_gid,
CopyFlags copy_flags) {
@ -492,6 +499,9 @@ static int fd_copy_directory(
assert(st);
assert(to);
if (depth_left == 0)
return -ENAMETOOLONG;
if (from)
fdf = openat(df, from, O_RDONLY|O_DIRECTORY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
else
@ -530,13 +540,40 @@ static int fd_copy_directory(
continue;
}
if (buf.st_dev != original_device)
continue;
if (S_ISDIR(buf.st_mode)) {
/*
* Don't descend into directories on other file systems, if this is requested. We do a simple
* .st_dev check here, which basically comes for free. Note that we do this check only on
* directories, not other kind of file system objects, for two reason:
*
* • The kernel's overlayfs pseudo file system that overlays multiple real file systems
* propagates the .st_dev field of the file system a file originates from all the way up
* through the stack to stat(). It doesn't do that for directories however. This means that
* comparing .st_dev on non-directories suggests that they all are mount points. To avoid
* confusion we hence avoid relying on this check for regular files.
*
* • The main reason we do this check at all is to protect ourselves from bind mount cycles,
* where we really want to avoid descending down in all eternity. However the .st_dev check
* is usually not sufficient for this protection anyway, as bind mount cycles from the same
* file system onto itself can't be detected that way. (Note we also do a recursion depth
* check, which is probably the better protection in this regard, which is why
* COPY_SAME_MOUNT is optional).
*/
if (S_ISREG(buf.st_mode))
if (FLAGS_SET(copy_flags, COPY_SAME_MOUNT)) {
if (buf.st_dev != original_device)
continue;
r = fd_is_mount_point(dirfd(d), de->d_name, 0);
if (r < 0)
return r;
if (r > 0)
continue;
}
q = fd_copy_directory(dirfd(d), de->d_name, &buf, fdt, de->d_name, original_device, depth_left-1, override_uid, override_gid, copy_flags);
} else if (S_ISREG(buf.st_mode))
q = fd_copy_regular(dirfd(d), de->d_name, &buf, fdt, de->d_name, override_uid, override_gid, copy_flags);
else if (S_ISDIR(buf.st_mode))
q = fd_copy_directory(dirfd(d), de->d_name, &buf, fdt, de->d_name, original_device, override_uid, override_gid, copy_flags);
else if (S_ISLNK(buf.st_mode))
q = fd_copy_symlink(dirfd(d), de->d_name, &buf, fdt, de->d_name, override_uid, override_gid, copy_flags);
else if (S_ISFIFO(buf.st_mode))
@ -586,7 +623,7 @@ int copy_tree_at(int fdf, const char *from, int fdt, const char *to, uid_t overr
if (S_ISREG(st.st_mode))
return fd_copy_regular(fdf, from, &st, fdt, to, override_uid, override_gid, copy_flags);
else if (S_ISDIR(st.st_mode))
return fd_copy_directory(fdf, from, &st, fdt, to, st.st_dev, override_uid, override_gid, copy_flags);
return fd_copy_directory(fdf, from, &st, fdt, to, st.st_dev, COPY_DEPTH_MAX, override_uid, override_gid, copy_flags);
else if (S_ISLNK(st.st_mode))
return fd_copy_symlink(fdf, from, &st, fdt, to, override_uid, override_gid, copy_flags);
else if (S_ISFIFO(st.st_mode))
@ -613,7 +650,7 @@ int copy_directory_fd(int dirfd, const char *to, CopyFlags copy_flags) {
if (!S_ISDIR(st.st_mode))
return -ENOTDIR;
return fd_copy_directory(dirfd, NULL, &st, AT_FDCWD, to, st.st_dev, UID_INVALID, GID_INVALID, copy_flags);
return fd_copy_directory(dirfd, NULL, &st, AT_FDCWD, to, st.st_dev, COPY_DEPTH_MAX, UID_INVALID, GID_INVALID, copy_flags);
}
int copy_directory(const char *from, const char *to, CopyFlags copy_flags) {
@ -628,7 +665,7 @@ int copy_directory(const char *from, const char *to, CopyFlags copy_flags) {
if (!S_ISDIR(st.st_mode))
return -ENOTDIR;
return fd_copy_directory(AT_FDCWD, from, &st, AT_FDCWD, to, st.st_dev, UID_INVALID, GID_INVALID, copy_flags);
return fd_copy_directory(AT_FDCWD, from, &st, AT_FDCWD, to, st.st_dev, COPY_DEPTH_MAX, UID_INVALID, GID_INVALID, copy_flags);
}
int copy_file_fd(const char *from, int fdt, CopyFlags copy_flags) {

7
src/basic/copy.h
View file

@ -13,9 +13,10 @@
#include <sys/types.h>
typedef enum CopyFlags {
COPY_REFLINK = 1U << 0, /* Try to reflink */
COPY_MERGE = 1U << 1, /* Merge existing trees with our new one to copy */
COPY_REPLACE = 1U << 2, /* Replace an existing file if there's one */
COPY_REFLINK = 1U << 0, /* Try to reflink */
COPY_MERGE = 1U << 1, /* Merge existing trees with our new one to copy */
COPY_REPLACE = 1U << 2, /* Replace an existing file if there's one */
COPY_SAME_MOUNT = 1U << 3, /* Don't descend recursively into other file systems, across mount point boundaries */
} CopyFlags;
int copy_file_fd(const char *from, int to, CopyFlags copy_flags);