FEXECVE(3) Linux Programmer's Manual FEXECVE(3)
fexecve - execute program specified via file descriptor
int fexecve(int fd, char *const argv, char *const envp);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
Since glibc 2.10:
_XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L
Before glibc 2.10:
fexecve() performs the same task as execve(2), with the difference that the file to be
executed is specified via a file descriptor, fd, rather than via a pathname. The file
descriptor fd must be opened read-only, and the caller must have permission to execute the
file that it refers to.
A successful call to fexecve() never returns. On error, the function returns, with a
result value of -1, and errno is set appropriately.
Errors are as for execve(2), with the following additions:
EINVAL fd is not a valid file descriptor, or argv is NULL, or envp is NULL.
ENOSYS The /proc filesystem could not be accessed.
fexecve() is implemented since glibc 2.3.2.
POSIX.1-2008. This function is not specified in POSIX.1-2001, and is not widely available
on other systems. It is specified in POSIX.1-2008.
On Linux, fexecve() is implemented using the proc(5) filesystem, so /proc needs to be
mounted and available at the time of the call.
The idea behind fexecve() is to allow the caller to verify (checksum) the contents of an
executable before executing it. Simply opening the file, checksumming the contents, and
then doing an execve(2) would not suffice, since, between the two steps, the filename, or
a directory prefix of the pathname, could have been exchanged (by, for example, modifying
the target of a symbolic link). fexecve() does not mitigate the problem that the contents
of a file could be changed between the checksumming and the call to fexecve(); for that,
the solution is to ensure that the permissions on the file prevent it from being modified
by malicious users.
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Linux 2013-10-25 FEXECVE(3)