fs/pipe.c: return error code rather than 0 in pipe_write()
pipe_write() would return 0 if it failed to merge the beginning of the data to write with the last, partially filled pipe buffer. It should return an error code instead. Userspace programs could be confused by write() returning 0 when called with a nonzero 'count'. The EFAULT error case was a regression from f0d1bec9 ("new helper: copy_page_from_iter()"), while the ops->confirm() error case was a much older bug. Test program: #include <assert.h> #include <errno.h> #include <unistd.h> int main(void) { int fd[2]; char data[1] = {0}; assert(0 == pipe(fd)); assert(1 == write(fd[1], data, 1)); /* prior to this patch, write() returned 0 here */ assert(-1 == write(fd[1], NULL, 1)); assert(errno == EFAULT); } Cc: stable@vger.kernel.org # at least v3.15+ Signed-off-by: Eric Biggers <ebiggers3@gmail.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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