Brad Bishop | 1a4b7ee | 2018-12-16 17:11:34 -0800 | [diff] [blame^] | 1 | From 91bb4f5c9c11464468e8d3fa4746d98d59997264 Mon Sep 17 00:00:00 2001 |
| 2 | From: Andre McCurdy <armccurdy@gmail.com> |
| 3 | Date: Tue, 10 Oct 2017 14:33:30 -0700 |
| 4 | Subject: [PATCH 17/19] don't pass AT_SYMLINK_NOFOLLOW flag to faccessat() |
| 5 | |
| 6 | Avoid using AT_SYMLINK_NOFOLLOW flag. It doesn't seem like the right |
| 7 | thing to do and it's not portable (not supported by musl). See: |
| 8 | |
| 9 | http://lists.landley.net/pipermail/toybox-landley.net/2014-September/003610.html |
| 10 | http://www.openwall.com/lists/musl/2015/02/05/2 |
| 11 | |
| 12 | Note that laccess() is never passing AT_EACCESS so a lot of the |
| 13 | discussion in the links above doesn't apply. Note also that |
| 14 | (currently) all systemd callers of laccess() pass mode as F_OK, so |
| 15 | only check for existence of a file, not access permissions. |
| 16 | Therefore, in this case, the only distiction between faccessat() |
| 17 | with (flag == 0) and (flag == AT_SYMLINK_NOFOLLOW) is the behaviour |
| 18 | for broken symlinks; laccess() on a broken symlink will succeed with |
| 19 | (flag == AT_SYMLINK_NOFOLLOW) and fail (flag == 0). |
| 20 | |
| 21 | The laccess() macros was added to systemd some time ago and it's not |
| 22 | clear if or why it needs to return success for broken symlinks. Maybe |
| 23 | just historical and not actually necessary or desired behaviour? |
| 24 | |
| 25 | Upstream-Status: Inappropriate [musl specific] |
| 26 | |
| 27 | Signed-off-by: Andre McCurdy <armccurdy@gmail.com> |
| 28 | --- |
| 29 | src/basic/fs-util.h | 22 +++++++++++++++++++++- |
| 30 | src/shared/base-filesystem.c | 6 +++--- |
| 31 | 2 files changed, 24 insertions(+), 4 deletions(-) |
| 32 | |
| 33 | diff --git a/src/basic/fs-util.h b/src/basic/fs-util.h |
| 34 | index 28566773c..14b864cc5 100644 |
| 35 | --- a/src/basic/fs-util.h |
| 36 | +++ b/src/basic/fs-util.h |
| 37 | @@ -32,7 +32,27 @@ int fchmod_opath(int fd, mode_t m); |
| 38 | |
| 39 | int fd_warn_permissions(const char *path, int fd); |
| 40 | |
| 41 | -#define laccess(path, mode) faccessat(AT_FDCWD, (path), (mode), AT_SYMLINK_NOFOLLOW) |
| 42 | +/* |
| 43 | + Avoid using AT_SYMLINK_NOFOLLOW flag. It doesn't seem like the right thing to |
| 44 | + do and it's not portable (not supported by musl). See: |
| 45 | + |
| 46 | + http://lists.landley.net/pipermail/toybox-landley.net/2014-September/003610.html |
| 47 | + http://www.openwall.com/lists/musl/2015/02/05/2 |
| 48 | + |
| 49 | + Note that laccess() is never passing AT_EACCESS so a lot of the discussion in |
| 50 | + the links above doesn't apply. Note also that (currently) all systemd callers |
| 51 | + of laccess() pass mode as F_OK, so only check for existence of a file, not |
| 52 | + access permissions. Therefore, in this case, the only distiction between |
| 53 | + faccessat() with (flag == 0) and (flag == AT_SYMLINK_NOFOLLOW) is the |
| 54 | + behaviour for broken symlinks; laccess() on a broken symlink will succeed |
| 55 | + with (flag == AT_SYMLINK_NOFOLLOW) and fail (flag == 0). |
| 56 | + |
| 57 | + The laccess() macros was added to systemd some time ago and it's not clear if |
| 58 | + or why it needs to return success for broken symlinks. Maybe just historical |
| 59 | + and not actually necessary or desired behaviour? |
| 60 | +*/ |
| 61 | + |
| 62 | +#define laccess(path, mode) faccessat(AT_FDCWD, (path), (mode), 0) |
| 63 | |
| 64 | int touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gid, mode_t mode); |
| 65 | int touch(const char *path); |
| 66 | diff --git a/src/shared/base-filesystem.c b/src/shared/base-filesystem.c |
| 67 | index 89d7a7d59..34b4ad53a 100644 |
| 68 | --- a/src/shared/base-filesystem.c |
| 69 | +++ b/src/shared/base-filesystem.c |
| 70 | @@ -53,7 +53,7 @@ int base_filesystem_create(const char *root, uid_t uid, gid_t gid) { |
| 71 | return log_error_errno(errno, "Failed to open root file system: %m"); |
| 72 | |
| 73 | for (i = 0; i < ELEMENTSOF(table); i ++) { |
| 74 | - if (faccessat(fd, table[i].dir, F_OK, AT_SYMLINK_NOFOLLOW) >= 0) |
| 75 | + if (faccessat(fd, table[i].dir, F_OK, 0) >= 0) |
| 76 | continue; |
| 77 | |
| 78 | if (table[i].target) { |
| 79 | @@ -61,7 +61,7 @@ int base_filesystem_create(const char *root, uid_t uid, gid_t gid) { |
| 80 | |
| 81 | /* check if one of the targets exists */ |
| 82 | NULSTR_FOREACH(s, table[i].target) { |
| 83 | - if (faccessat(fd, s, F_OK, AT_SYMLINK_NOFOLLOW) < 0) |
| 84 | + if (faccessat(fd, s, F_OK, 0) < 0) |
| 85 | continue; |
| 86 | |
| 87 | /* check if a specific file exists at the target path */ |
| 88 | @@ -72,7 +72,7 @@ int base_filesystem_create(const char *root, uid_t uid, gid_t gid) { |
| 89 | if (!p) |
| 90 | return log_oom(); |
| 91 | |
| 92 | - if (faccessat(fd, p, F_OK, AT_SYMLINK_NOFOLLOW) < 0) |
| 93 | + if (faccessat(fd, p, F_OK, 0) < 0) |
| 94 | continue; |
| 95 | } |
| 96 | |
| 97 | -- |
| 98 | 2.11.0 |
| 99 | |