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Merge pull request #7436 from poettering/mount-util-fixup

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mount-util.c fixes regarding name_to_handle_at()
This commit is contained in:
Lennart Poettering
2017-11-23 21:01:12 +01:00
committed by GitHub
parent 8dc787d185 9b1573ef76
commit e2cd893bda
2 changed files with 36 additions and 37 deletions
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src/basic/mount-util.c
+18 -16
View File
@@ -65,7 +65,6 @@ int name_to_handle_at_loop(
for (;;) {
int mnt_id = -1;
size_t m;
if (name_to_handle_at(fd, path, h, &mnt_id, flags) >= 0) {
@@ -84,22 +83,24 @@ int name_to_handle_at_loop(
if (!ret_handle && ret_mnt_id && mnt_id >= 0) {
/* As it appears, name_to_handle_at() fills in mnt_id even when it returns EOVERFLOW, but
* that's undocumented. Hence, let's make use of this if it appears to be filled in, and the
* caller was interested in only the mount ID an nothing else. */
/* As it appears, name_to_handle_at() fills in mnt_id even when it returns EOVERFLOW when the
* buffer is too small, but that's undocumented. Hence, let's make use of this if it appears to
* be filled in, and the caller was interested in only the mount ID an nothing else. */
*ret_mnt_id = mnt_id;
return 0;
}
/* The buffer was too small. Size the new buffer by what name_to_handle_at() returned, but make sure it
* is always larger than what we passed in before */
m = h->handle_bytes > n ? h->handle_bytes : n * 2;
if (m < n) /* Check for multiplication overflow */
/* If name_to_handle_at() didn't increase the byte size, then this EOVERFLOW is caused by something
* else (apparently EOVERFLOW is returned for untriggered nfs4 mounts sometimes), not by the too small
* buffer. In that case propagate EOVERFLOW */
if (h->handle_bytes <= n)
return -EOVERFLOW;
if (offsetof(struct file_handle, f_handle) + m < m) /* check for addition overflow */
/* The buffer was too small. Size the new buffer by what name_to_handle_at() returned. */
n = h->handle_bytes;
if (offsetof(struct file_handle, f_handle) + n < n) /* check for addition overflow */
return -EOVERFLOW;
n = m;
free(h);
h = malloc0(offsetof(struct file_handle, f_handle) + n);
@@ -131,7 +132,7 @@ static int fd_fdinfo_mnt_id(int fd, const char *filename, int flags, int *mnt_id
if (r == -ENOENT) /* The fdinfo directory is a relatively new addition */
return -EOPNOTSUPP;
if (r < 0)
return -errno;
return r;
p = startswith(fdinfo, "mnt_id:");
if (!p) {
@@ -182,9 +183,10 @@ int fd_is_mount_point(int fd, const char *filename, int flags) {
* real mounts of their own. */
r = name_to_handle_at_loop(fd, filename, &h, &mount_id, flags);
if (IN_SET(r, -ENOSYS, -EACCES, -EPERM))
/* This kernel does not support name_to_handle_at() at all, or the syscall was blocked (maybe through
* seccomp, because we are running inside of a container?): fall back to simpler logic. */
if (IN_SET(r, -ENOSYS, -EACCES, -EPERM, -EOVERFLOW))
/* This kernel does not support name_to_handle_at() at all (ENOSYS), or the syscall was blocked
* (EACCES/EPERM; maybe through seccomp, because we are running inside of a container?), or the mount
* point is not triggered yet (EOVERFLOW, thinkg nfs4): fall back to simpler logic. */
goto fallback_fdinfo;
else if (r == -EOPNOTSUPP)
/* This kernel or file system does not support name_to_handle_at(), hence let's see if the upper fs
@@ -204,7 +206,7 @@ int fd_is_mount_point(int fd, const char *filename, int flags) {
* it must be a mount point. */
return 1;
} else if (r < 0)
return r;
return r;
/* The parent can do name_to_handle_at() but the
* directory we are interested in can't? If so, it
@@ -306,7 +308,7 @@ int path_get_mnt_id(const char *path, int *ret) {
int r;
r = name_to_handle_at_loop(AT_FDCWD, path, NULL, ret, 0);
if (IN_SET(r, -EOPNOTSUPP, -ENOSYS, -EACCES, -EPERM)) /* kernel/fs don't support this, or seccomp blocks access */
if (IN_SET(r, -EOPNOTSUPP, -ENOSYS, -EACCES, -EPERM, -EOVERFLOW)) /* kernel/fs don't support this, or seccomp blocks access, or untriggered mount */
return fd_fdinfo_mnt_id(AT_FDCWD, path, 0, ret);
return r;
src/test/test-mount-util.c
+18 -21
View File
@@ -27,6 +27,7 @@
#include "hashmap.h"
#include "log.h"
#include "mount-util.h"
#include "path-util.h"
#include "string-util.h"
static void test_mount_propagation_flags(const char *name, int ret, unsigned long expected) {
@@ -51,16 +52,15 @@ static void test_mnt_id(void) {
_cleanup_fclose_ FILE *f = NULL;
Hashmap *h;
Iterator i;
char *k;
void *p;
char *p;
void *k;
int r;
assert_se(f = fopen("/proc/self/mountinfo", "re"));
assert_se(h = hashmap_new(&string_hash_ops));
assert_se(h = hashmap_new(&trivial_hash_ops));
for (;;) {
_cleanup_free_ char *line = NULL, *path = NULL;
void *old_key;
int mnt_id;
r = read_line(f, LONG_LINE_MAX, &line);
@@ -70,38 +70,35 @@ static void test_mnt_id(void) {
assert_se(sscanf(line, "%i %*s %*s %*s %ms", &mnt_id, &path) == 2);
/* Add all mount points and their ids to a hashtable, so that we filter out mount points that are
* overmounted. For those we only care for the "upper" mount, since that's the only one
* path_get_mnt_id() can determine. */
if (hashmap_remove2(h, path, &old_key))
free(old_key);
assert_se(hashmap_put(h, path, INT_TO_PTR(mnt_id)) >= 0);
assert_se(hashmap_put(h, INT_TO_PTR(mnt_id), path) >= 0);
path = NULL;
}
HASHMAP_FOREACH_KEY(p, k, h, i) {
int mnt_id = PTR_TO_INT(p), mnt_id2;
int mnt_id = PTR_TO_INT(k), mnt_id2;
r = path_get_mnt_id(k, &mnt_id2);
r = path_get_mnt_id(p, &mnt_id2);
if (r == -EOPNOTSUPP) { /* kernel or file system too old? */
log_debug("%s doesn't support mount IDs\n", k);
log_debug("%s doesn't support mount IDs\n", p);
continue;
}
if (IN_SET(r, -EACCES, -EPERM)) {
log_debug("Can't access %s\n", k);
log_debug("Can't access %s\n", p);
continue;
}
log_debug("mnt id of %s is %i\n", k, mnt_id2);
log_debug("mnt id of %s is %i\n", p, mnt_id2);
assert_se(r >= 0);
assert_se(mnt_id == mnt_id2);
if (mnt_id == mnt_id2)
continue;
/* The ids don't match? If so, then there are two mounts on the same path, let's check if that's really
* the case */
assert_se(path_equal_ptr(hashmap_get(h, INT_TO_PTR(mnt_id2)), p));
}
while ((k = hashmap_steal_first_key(h)))
free(k);
while ((p = hashmap_steal_first(h)))
free(p);
hashmap_free(h);
}