commit: 9b81814db56a02384e40f6e19576a4e9777628ac
Author: Mike Frysinger <vapier <AT> gentoo <DOT> org>
AuthorDate: Sat Oct 23 06:39:35 2021 +0000
Commit: Mike Frysinger <vapier <AT> gentoo <DOT> org>
CommitDate: Sat Oct 23 22:18:03 2021 +0000
URL: https://gitweb.gentoo.org/proj/sandbox.git/commit/?id=9b81814d
libsandbox: fix flags extraction for a few syscalls
While many syscalls follow similar patterns for dirfd & path handling,
the flags argument is less consistent -- it tends to be last with all
other arguments in between. As a result, a few syscalls were pulling
the wrong argument for the flags settings:
* fchmodat: the syscall interface has no flags at all
* fchownat: the flags come after uid & gid
* utimensat: the flags come after the timespec
These syscalls haven't been a problem in practice because no one ever
tries to chmod/chown/utimes on symlinks themselves.
Signed-off-by: Mike Frysinger <vapier <AT> gentoo.org>
libsandbox/trace.c | 21 ++++++++++++++-------
1 file changed, 14 insertions(+), 7 deletions(-)
diff --git a/libsandbox/trace.c b/libsandbox/trace.c
index 89bd591..7660d47 100644
--- a/libsandbox/trace.c
+++ b/libsandbox/trace.c
@@ -217,6 +217,7 @@ struct syscall_state {
bool (*pre_check)(const char *func, const char *pathname, int dirfd);
};
+/* Check syscall that only takes a path as its |ibase| argument. */
static bool _trace_check_syscall_C(struct syscall_state *state, int ibase)
{
char *path = do_peekstr(trace_arg(state->regs, ibase));
@@ -233,6 +234,7 @@ static bool _trace_check_syscall_C(struct syscall_state
*state, int ibase)
free(path);
return ret;
}
+/* Check syscall that only takes a path as its first argument. */
static bool trace_check_syscall_C(struct syscall_state *state)
{
return _trace_check_syscall_C(state, 1);
@@ -255,20 +257,24 @@ static bool __trace_check_syscall_DCF(struct
syscall_state *state, int ibase, in
free(path);
return ret;
}
-static bool _trace_check_syscall_DCF(struct syscall_state *state, int ibase)
+/* Check syscall that takes a dirfd & path starting at |ibase| argument, and
flags at |fbase|. */
+static bool _trace_check_syscall_DCF(struct syscall_state *state, int ibase,
int fbase)
{
- int flags = trace_arg(state->regs, ibase + 2);
+ int flags = trace_arg(state->regs, fbase);
return __trace_check_syscall_DCF(state, ibase, flags);
}
+/* Check syscall that takes a dirfd, path, and flags as its first 3 arguments.
*/
static bool trace_check_syscall_DCF(struct syscall_state *state)
{
- return _trace_check_syscall_DCF(state, 1);
+ return _trace_check_syscall_DCF(state, 1, 3);
}
+/* Check syscall that takes a dirfd & path starting at |ibase| argument. */
static bool _trace_check_syscall_DC(struct syscall_state *state, int ibase)
{
return __trace_check_syscall_DCF(state, ibase, 0);
}
+/* Check syscall that takes a dirfd & path as its first 2 arguments (but no
flags). */
static bool trace_check_syscall_DC(struct syscall_state *state)
{
return _trace_check_syscall_DC(state, 1);
@@ -311,12 +317,13 @@ static bool trace_check_syscall(const struct
syscall_entry *se, void *regs)
else if (nr == SB_NR_CHMOD) return trace_check_syscall_C (&state);
else if (nr == SB_NR_CHOWN) return trace_check_syscall_C (&state);
else if (nr == SB_NR_CREAT) return trace_check_syscall_C (&state);
- else if (nr == SB_NR_FCHMODAT) return trace_check_syscall_DCF(&state);
- else if (nr == SB_NR_FCHOWNAT) return trace_check_syscall_DCF(&state);
+ /* NB: Linux syscall does not have a flags argument. */
+ else if (nr == SB_NR_FCHMODAT) return trace_check_syscall_DC (&state);
+ else if (nr == SB_NR_FCHOWNAT) return _trace_check_syscall_DCF(&state,
1, 5);
else if (nr == SB_NR_FUTIMESAT) return trace_check_syscall_DC (&state);
else if (nr == SB_NR_LCHOWN) return trace_check_syscall_C (&state);
else if (nr == SB_NR_LINK) return _trace_check_syscall_C (&state,
2);
- else if (nr == SB_NR_LINKAT) return _trace_check_syscall_DCF(&state,
3);
+ else if (nr == SB_NR_LINKAT) return _trace_check_syscall_DCF(&state,
3, 5);
else if (nr == SB_NR_MKDIR) return trace_check_syscall_C (&state);
else if (nr == SB_NR_MKDIRAT) return trace_check_syscall_DC (&state);
else if (nr == SB_NR_MKNOD) return trace_check_syscall_C (&state);
@@ -336,7 +343,7 @@ static bool trace_check_syscall(const struct syscall_entry
*se, void *regs)
else if (nr == SB_NR_UNLINKAT) return trace_check_syscall_DCF(&state);
else if (nr == SB_NR_UTIME) return trace_check_syscall_C (&state);
else if (nr == SB_NR_UTIMES) return trace_check_syscall_C (&state);
- else if (nr == SB_NR_UTIMENSAT) return _trace_check_syscall_DCF(&state,
1);
+ else if (nr == SB_NR_UTIMENSAT) return _trace_check_syscall_DCF(&state,
1, 4);
else if (nr == SB_NR_ACCESS) {
char *path = do_peekstr(trace_arg(regs, 1));
