From 8e03235147a9e774d3ba084e93c2da1aa94d1cec Mon Sep 17 00:00:00 2001 From: Siddhesh Poyarekar Date: Mon, 22 Feb 2021 20:45:50 +0530 Subject: [PATCH] binutils: Avoid renaming over existing files Renaming over existing files needs additional care to restore permissions and ownership, which may not always succeed. Additionally, other properties of the file such as extended attributes may be lost, making the operation flaky. For predictable results, resort to rename() only if the file does not exist, otherwise copy the file contents into the existing file. This ensures that no additional tricks are needed to retain file properties. This also allows dropping of the redundant set_times on the tmpfile in objcopy/strip since now we no longer rename over existing files. binutils/ * ar.c (write_archive): Adjust call to SMART_RENAME. * arsup.c (ar_save): Likewise. * objcopy (strip_main): Don't set times on temporary file and adjust call to SMART_RENAME. (copy_main): Likewise. * rename.c [!S_ISLNK]: Remove definitions. (try_preserve_permissions): Remove function. (smart_rename): Replace PRESERVE_DATES argument with TARGET_STAT. Use rename system call only if TO does not exist. * bucomm.h (smart_rename): Adjust declaration. (cherry picked from commit 3685de750e6a091663a0abe42528cad29e960e35) Upstream-Status: Backport [https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=8e03235147a9e774d3ba084e93c2da1aa94d1cec] CVE: CVE-2021-20197 Signed-off-by: Vinay Kumar --- binutils/ar.c | 2 +- binutils/arsup.c | 2 +- binutils/bucomm.h | 3 ++- binutils/objcopy.c | 8 ++----- binutils/rename.c | 55 +++++++++------------------------------------- 6 files changed, 29 insertions(+), 54 deletions(-) diff --git a/binutils/ar.c b/binutils/ar.c index 45a34e3a6cf..3a91708b51c 100644 --- a/binutils/ar.c +++ b/binutils/ar.c @@ -1308,7 +1308,7 @@ write_archive (bfd *iarch) /* We don't care if this fails; we might be creating the archive. */ bfd_close (iarch); - if (smart_rename (new_name, old_name, 0) != 0) + if (smart_rename (new_name, old_name, NULL) != 0) xexit (1); free (old_name); free (new_name); diff --git a/binutils/arsup.c b/binutils/arsup.c index 5403a0c5d74..0a1f63f6456 100644 --- a/binutils/arsup.c +++ b/binutils/arsup.c @@ -351,7 +351,7 @@ ar_save (void) bfd_close (obfd); - smart_rename (ofilename, real_name, 0); + smart_rename (ofilename, real_name, NULL); obfd = 0; free (ofilename); } diff --git a/binutils/bucomm.h b/binutils/bucomm.h index 91f6a5b228f..aa7e33d8cd1 100644 --- a/binutils/bucomm.h +++ b/binutils/bucomm.h @@ -71,7 +71,8 @@ extern void print_version (const char *); /* In rename.c. */ extern void set_times (const char *, const struct stat *); -extern int smart_rename (const char *, const char *, int); +extern int smart_rename (const char *, const char *, struct stat *); + /* In libiberty. */ void *xmalloc (size_t); diff --git a/binutils/objcopy.c b/binutils/objcopy.c index eab3b6db585..07a872b5a80 100644 --- a/binutils/objcopy.c +++ b/binutils/objcopy.c @@ -4861,12 +4861,10 @@ strip_main (int argc, char *argv[]) output_target, NULL); if (status == 0) { - if (preserve_dates) - set_times (tmpname, &statbuf); if (output_file != tmpname) status = (smart_rename (tmpname, output_file ? output_file : argv[i], - preserve_dates) != 0); + preserve_dates ? &statbuf : NULL) != 0); if (status == 0) status = hold_status; } @@ -5931,11 +5929,9 @@ copy_main (int argc, char *argv[]) output_target, input_arch); if (status == 0) { - if (preserve_dates) - set_times (tmpname, &statbuf); if (tmpname != output_filename) status = (smart_rename (tmpname, input_filename, - preserve_dates) != 0); + preserve_dates ? &statbuf : NULL) != 0); } else unlink_if_ordinary (tmpname); diff --git a/binutils/rename.c b/binutils/rename.c index 65ad5bf52c4..f471b45fd3f 100644 --- a/binutils/rename.c +++ b/binutils/rename.c @@ -122,20 +122,13 @@ set_times (const char *destination, const struct stat *statbuf) non_fatal (_("%s: cannot set time: %s"), destination, strerror (errno)); } -#ifndef S_ISLNK -#ifdef S_IFLNK -#define S_ISLNK(m) (((m) & S_IFMT) == S_IFLNK) -#else -#define S_ISLNK(m) 0 -#define lstat stat -#endif -#endif - -/* Rename FROM to TO, copying if TO is a link. - Return 0 if ok, -1 if error. */ +/* Rename FROM to TO, copying if TO exists. TARGET_STAT has the file status + that, if non-NULL, is used to fix up timestamps after rename. Return 0 if + ok, -1 if error. */ int -smart_rename (const char *from, const char *to, int preserve_dates ATTRIBUTE_UNUSED) +smart_rename (const char *from, const char *to, + struct stat *target_stat ATTRIBUTE_UNUSED) { bfd_boolean exists; struct stat s; @@ -158,38 +151,10 @@ smart_rename (const char *from, const char *to, int preserve_dates ATTRIBUTE_UNU unlink (from); } #else - /* Use rename only if TO is not a symbolic link and has - only one hard link, and we have permission to write to it. */ - if (! exists - || (!S_ISLNK (s.st_mode) - && S_ISREG (s.st_mode) - && (s.st_mode & S_IWUSR) - && s.st_nlink == 1) - ) + /* Avoid a full copy and use rename if TO does not exist. */ + if (!exists) { - ret = rename (from, to); - if (ret == 0) - { - if (exists) - { - /* Try to preserve the permission bits and ownership of - TO. First get the mode right except for the setuid - bit. Then change the ownership. Then fix the setuid - bit. We do the chmod before the chown because if the - chown succeeds, and we are a normal user, we won't be - able to do the chmod afterward. We don't bother to - fix the setuid bit first because that might introduce - a fleeting security problem, and because the chown - will clear the setuid bit anyhow. We only fix the - setuid bit if the chown succeeds, because we don't - want to introduce an unexpected setuid file owned by - the user running objcopy. */ - chmod (to, s.st_mode & 0777); - if (chown (to, s.st_uid, s.st_gid) >= 0) - chmod (to, s.st_mode & 07777); - } - } - else + if ((ret = rename (from, to)) != 0) { /* We have to clean up here. */ non_fatal (_("unable to rename '%s'; reason: %s"), to, strerror (errno)); @@ -202,8 +167,8 @@ smart_rename (const char *from, const char *to, int preserve_dates ATTRIBUTE_UNU if (ret != 0) non_fatal (_("unable to copy file '%s'; reason: %s"), to, strerror (errno)); - if (preserve_dates) - set_times (to, &s); + if (target_stat != NULL) + set_times (to, target_stat); unlink (from); } #endif /* _WIN32 && !__CYGWIN32__ */ -- 2.31.1