This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed- bionic' to 'verification-done-bionic'. If the problem still exists, change the tag 'verification-needed-bionic' to 'verification-failed- bionic'.
If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you! ** Tags added: verification-needed-bionic -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1789746 Title: getxattr: always handle namespaced attributes Status in linux package in Ubuntu: Fix Released Status in linux source package in Xenial: Fix Committed Status in linux source package in Bionic: Fix Committed Status in linux source package in Cosmic: Fix Released Bug description: == SRU Justification == When running in a container with a user namespace, if you call getxattr with name = "system.posix_acl_access" and size % 8 != 4, then getxattr silently skips the user namespace fixup that it normally does resulting in un-fixed-up data being returned. This is caused by posix_acl_fix_xattr_to_user() being passed the total buffer size and not the actual size of the xattr as returned by vfs_getxattr(). I have pushed a commit upstream that fixes this bug: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=82c9a927bc5df6e06b72d206d24a9d10cced4eb5 This commit passes the actual length of the xattr as returned by vfs_getxattr() down. A reproducer for the issue is: touch acl_posix setfacl -m user:0:rwx acl_posix and the compile: #define _GNU_SOURCE #include <errno.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <unistd.h> #include <attr/xattr.h> /* Run in user namespace with nsuid 0 mapped to uid != 0 on the host. */ int main(int argc, void **argv) { ssize_t ret1, ret2; char buf1[128], buf2[132]; int fret = EXIT_SUCCESS; char *file; if (argc < 2) { fprintf(stderr, "Please specify a file with " "\"system.posix_acl_access\" permissions set\n"); _exit(EXIT_FAILURE); } file = argv[1]; ret1 = getxattr(file, "system.posix_acl_access", buf1, sizeof(buf1)); if (ret1 < 0) { fprintf(stderr, "%s - Failed to retrieve " "\"system.posix_acl_access\" " "from \"%s\"\n", strerror(errno), file); _exit(EXIT_FAILURE); } ret2 = getxattr(file, "system.posix_acl_access", buf2, sizeof(buf2)); if (ret2 < 0) { fprintf(stderr, "%s - Failed to retrieve " "\"system.posix_acl_access\" " "from \"%s\"\n", strerror(errno), file); _exit(EXIT_FAILURE); } if (ret1 != ret2) { fprintf(stderr, "The value of \"system.posix_acl_" "access\" for file \"%s\" changed " "between two successive calls\n", file); _exit(EXIT_FAILURE); } for (ssize_t i = 0; i < ret2; i++) { if (buf1[i] == buf2[i]) continue; fprintf(stderr, "Unexpected different in byte %zd: " "%02x != %02x\n", i, buf1[i], buf2[i]); fret = EXIT_FAILURE; } if (fret == EXIT_SUCCESS) fprintf(stderr, "Test passed\n"); else fprintf(stderr, "Test failed\n"); _exit(fret); } and run: ./tester acl_posix On a non-fixed up kernel this should return something like: root@c1:/# ./t Unexpected different in byte 16: ffffffa0 != 00 Unexpected different in byte 17: ffffff86 != 00 Unexpected different in byte 18: 01 != 00 and on a fixed kernel: root@c1:~# ./t Test passed == Fix == 82c9a927bc5d ("getxattr: use correct xattr length") == Regression Potential == Low. One liner that passes the actual length of the xattr as returned by vfs_getxattr() down. == Test Case == A test kernel was built with this patch and tested by the original bug reporter. The bug reporter states the test kernel resolved the bug. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1789746/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
